Package man-pages

Linux kernel and C library user-space interface documentation

http://www.kernel.org/doc/man-pages/

A large collection of manual pages from the Linux Documentation Project (LDP).

POSIX Header Files (Section 0p)
aio.h
asynchronous input and output
arpa_inet.h
The <arpa/inet.h> header shall define the in_port_t and in_addr_t types as described in <netinet/in.h>. The <arpa/inet.h> header shall define the in_addr...
assert.h
The <assert.h> header shall define the assert() macro. It refers to the macro NDEBUG which is not defined in the header.
complex.h
complex arithmetic
cpio.h
cpio archive values
ctype.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
dirent.h
The internal format of directories is unspecified.
dlfcn.h
dynamic linking
errno.h
Some of the functionality described on this reference page extends the ISO C standard. Any conflict between the requirements described here and the ISO C...
fcntl.h
The <fcntl.h> header shall define the following symbolic constants for the cmd argument used by fcntl(). The values shall be unique and shall be suitable for...
fenv.h
floating-point environment
float.h
The characteristics of floating types are defined in terms of a model that describes a representation of floating-point numbers and values that provide...
fmtmsg.h
message display structures
fnmatch.h
filename-matching types
ftw.h
file tree traversal
glob.h
The <glob.h> header shall define the structures and symbolic constants used by the glob() function.
grp.h
group structure
iconv.h
codeset conversion facility
inttypes.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
iso646.h
alternative spellings
langinfo.h
The <langinfo.h> header shall define the symbolic constants used to identify items of langinfo data (see nl_langinfo()). The <langinfo.h> header shall define...
libgen.h
The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.
limits.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
locale.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
math.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
monetary.h
The <monetary.h> header shall define the locale_t type as described in <locale.h>. The <monetary.h> header shall define the size_t type as described in...
mqueue.h
The <mqueue.h> header shall define the mqd_t type, which is used for message queue descriptors. This is not an array type. The <mqueue.h> header shall define...
ndbm.h
definitions for ndbm database operations
netdb.h
The <netdb.h> header may define the in_port_t type and the in_addr_t type as described in <netinet/in.h>.
net_if.h
sockets local interfaces
netinet_in.h
Internet address family
netinet_tcp.h
definitions for the Internet Transmission Control Protocol (TCP)
nl_types.h
data types
poll.h
definitions for the poll() function
pthread.h
threads
pwd.h
password structure
regex.h
The <regex.h> header shall define the structures and symbolic constants used by the regcomp(), regexec(), regerror(), and regfree() functions.
sched.h
The <sched.h> header shall define the pid_t type as described in <sys/types.h>. The <sched.h> header shall define the time_t type as described in <sys/types.h>...
search.h
search tables
semaphore.h
The <semaphore.h> header shall define the sem_t type, used in performing semaphore operations. The semaphore may be implemented using a file descriptor, in...
setjmp.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
signal.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
spawn.h
The <spawn.h> header shall define the posix_spawnattr_t and posix_spawn_file_actions_t types used in performing spawn operations. The <spawn.h> header shall...
stdarg.h
The <stdarg.h> header shall contain a set of macros which allows portable functions that accept variable argument lists to be written. Functions that have...
stdbool.h
boolean type and values
stddef.h
standard type definitions
stdint.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
stdio.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
stdlib.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
string.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
strings.h
The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided for use with ISO C standard compilers.
stropts.h
STREAMS interface (STREAMS)
sys_ipc.h
The <sys/ipc.h> header is used by three mechanisms for XSI interprocess communication (IPC): messages, semaphores, and shared memory. All use a common structure...
syslog.h
definitions for system error logging
sys_mman.h
memory management declarations
sys_msg.h
XSI message queue structures
sys_resource.h
definitions for XSI resource operations
sys_select.h
select types
sys_sem.h
XSI semaphore facility
sys_shm.h
XSI shared memory facility
sys_socket.h
The <sys/socket.h> header shall define the socklen_t type, which is an integer type of width of at least 32 bits; see Application Usage. The <sys/socket.h>...
sys_stat.h
The <sys/stat.h> header shall define the structure of the data returned by the fstat(), lstat(), and stat() functions.
sys_statvfs.h
VFS File System information structure
sys_time.h
time types
sys_times.h
file access and modification times structure
sys_types.h
data types
sys_uio.h
definitions for vector I/O operations
sys_un.h
definitions for UNIX domain sockets
sys_utsname.h
system name structure
sys_wait.h
declarations for waiting
tar.h
The <tar.h> header shall define the following symbolic constants with the indicated values.
termios.h
The <termios.h> header shall contain the definitions used by the terminal I/O interfaces (see Chapter 11, General Terminal Interface for the structures and...
tgmath.h
The <tgmath.h> header shall include the headers <math.h> and <complex.h> and shall define several type-generic macros. Of the functions contained within the...
time.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
trace.h
tracing
ulimit.h
The <ulimit.h> header shall define the symbolic constants used by the ulimit() function.
unistd.h
The <unistd.h> header defines miscellaneous symbolic constants and types, and declares miscellaneous functions. The actual values of the constants are...
utime.h
access and modification times structure
utmpx.h
user accounting database definitions
wchar.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
wctype.h
Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see the...
wordexp.h
The <wordexp.h> header shall define the structures and symbolic constants used by the wordexp() and wordfree() functions.
General Commands (Section 1)
getent
The getent command displays entries from databases supported by the Name Service Switch libraries, which are configured in /etc/nsswitch.conf. If one or more...
iconv
The iconv program reads in text in one encoding and outputs the text in another encoding. If no input files are given, or if it is given as a dash (-), iconv...
intro
Section 1 of the manual describes user commands and tools, for example, file manipulation tools, shells, compilers, web browsers, file and image viewers and...
ldd
ldd prints the shared objects (shared libraries) required by each program or shared object specified on the command line.
locale
The locale command displays information about the current locale, or all locales, on standard output. When invoked without arguments, locale displays the...
localedef
The localedef program reads the indicated charmap and input files, compiles them to a binary form quickly usable by the locale functions in the C library...
memusage
memusage is a bash script which profiles memory usage of the program, program. It preloads the libmemusage.so library into the caller's environment (via the...
memusagestat
memusagestat creates a PNG file containing a graphical representation of the memory profiling data in the file datafile; that file is generated via the -d (or...
mtrace
mtrace is a Perl script used to interpret and provide human readable output of the trace log contained in the file mtracedata, whose contents were produced by...
pldd
The pldd command displays a list of the dynamic shared objects that are linked into the process with the specified process ID. The list includes the libraries...
sprof
The sprof command displays a profiling summary for the shared object (shared library) specified as its first command-line argument. The profiling summary is...
time
The time command runs the specified program command with the given arguments. When command finishes, time writes a message to standard error giving timing...
POSIX Commands (Section 1p)
alias
The alias utility shall create or redefine alias definitions or write the values of existing alias definitions to standard output. An alias definition provides...
ar
The ar utility is part of the Software Development Utilities option. The ar utility can be used to create and maintain groups of files combined into an archive...
asa
The asa utility shall write its input files to standard output, mapping carriage-control characters from the text files to line-printer control sequences in an...
at
The at utility shall read commands from standard input and group them together as an at-job, to be executed at a later time. The at-job shall be executed in a...
awk
The awk utility shall execute programs written in the awk programming language, which is specialized for textual data manipulation. An awk program is a sequence...
basename
The string operand shall be treated as a pathname, as defined in the Base Definitions volume of POSIX.1‐2008, Section 3.267, Pathname. The string string shall...
batch
The batch utility shall read commands from standard input and schedule them for execution in a batch queue.
bc
The bc utility shall implement an arbitrary precision calculator. It shall take input from any files given, then read from the standard input. If the standard...
bg
If job control is enabled (see the description of set -m), the bg utility shall resume suspended jobs from the current environment (see Section 2.12, Shell...
break
The break utility shall exit from the smallest enclosing for, while, or until loop, if any; or from the nth enclosing loop if n is specified. The value of n is...
c99
The c99 utility is an interface to the standard C compilation system; it shall accept source code conforming to the ISO C standard. The system conceptually...
cal
The cal utility shall write a calendar to standard output using the Julian calendar for dates from January 1, 1 through September 2, 1752 and the Gregorian...
cat
The cat utility shall read files in sequence and shall write their contents to the standard output in the same sequence.
cd
The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the...
cflow
The cflow utility shall analyze a collection of object files or assembler, C-language, lex, or yacc source files, and attempt to build a graph, written to...
chgrp
The chgrp utility shall set the group ID of the file named by each file operand to the group ID specified by the group operand.
chmod
The chmod utility shall change any or all of the file mode bits of the file named by each file operand in the way specified by the mode operand. It is...
chown
The chown utility shall set the user ID of the file named by each file operand to the user ID specified by the owner operand.
cksum
The cksum utility shall calculate and write to standard output a cyclic redundancy check (CRC) for each input file, and also write to standard output the number...
cmp
The cmp utility shall compare two files. The cmp utility shall write no output if the files are the same. Under default options, if they differ, it shall write...
colon
This utility shall only expand command arguments. It is used when a command is needed, as in the then condition of an if command, but nothing is to be done by...
comm
The comm utility shall read file1 and file2, which should be ordered in the current collating sequence, and produce three text columns as output: lines only in...
command
The command utility shall cause the shell to treat the arguments as a simple command, suppressing the shell function lookup that is described in Section...
compress
The compress utility shall attempt to reduce the size of the named files by using adaptive Lempel-Ziv coding algorithm.
continue
The continue utility shall return to the top of the smallest enclosing for, while, or until loop, or to the top of the nth enclosing loop, if n is specified...
cp
The first synopsis form is denoted by two operands, neither of which are existing files of type directory. The cp utility shall copy the contents of source_file...
crontab
The crontab utility shall create, replace, or edit a user's crontab entry; a crontab entry is a list of commands and the times at which they shall be executed...
csplit
The csplit utility shall read the file named by the file operand, write all or part of that file into other files as directed by the arg operands, and write the...
ctags
The ctags utility shall be provided on systems that support the the Software Development Utilities option, and either or both of the C-Language Development...
cut
The cut utility shall cut out bytes (-b option), characters (-c option), or character-delimited fields (-f option) from each line in one or more files...
cxref
The cxref utility shall analyze a collection of C-language files and attempt to build a cross-reference table. Information from #define lines shall be included...
date
The date utility shall write the date and time to standard output or attempt to set the system date and time. By default, the current date and time shall be...
dd
The dd utility shall copy the specified input file to the specified output file with possible conversions using specific input and output block sizes. It shall...
df
The df utility shall write the amount of available space and file slots for file systems on which the invoking user has appropriate read access. File systems...
diff
The diff utility shall compare the contents of file1 and file2 and write to standard output a list of changes necessary to convert file1 into file2. This list...
dirname
The string operand shall be treated as a pathname, as defined in the Base Definitions volume of POSIX.1‐2008, Section 3.267, Pathname.
dot
The shell shall execute commands from the file in the current environment. If file does not contain a <slash>, the shell shall use the search path specified by...
du
By default, the du utility shall write to standard output the size of the file space allocated to, and the size of the file space allocated to each subdirectory...
echo
The echo utility writes its arguments to standard output, followed by a <newline>. If there are no arguments, only the <newline> is written.
ed
The ed utility is a line-oriented text editor that uses two modes: command mode and input mode. In command mode the input characters shall be interpreted as...
env
The env utility shall obtain the current environment, modify it according to its arguments, then invoke the utility named by the utility operand with the...
eval
The eval utility shall construct a command by concatenating arguments together, separating each with a <space> character. The constructed command shall be read...
ex
The ex utility is a line-oriented text editor. There are two other modes of the editor—open and visual—in which screen-oriented editing is available. This is...
exec
The exec utility shall open, close, and/or copy file descriptors as specified by any redirections as part of the command. If exec is specified without command...
exit
The exit utility shall cause the shell to exit with the exit status specified by the unsigned decimal integer n. If n is specified, but its value is not between...
expand
The expand utility shall write files or the standard input to the standard output with <tab> characters replaced with one or more <space> characters needed to...
export
The shell shall give the export attribute to the variables corresponding to the specified names, which shall cause them to be in the environment of subsequently...
expr
The expr utility shall evaluate an expression and write the result to standard output.
false
The false utility shall return with a non-zero exit code.
fc
The fc utility shall list, or shall edit and re-execute, commands previously entered to an interactive sh. The command history list shall reference commands by...
fg
If job control is enabled (see the description of set -m), the fg utility shall move a background job from the current environment (see Section 2.12, Shell...
file
determine file type
find
The find utility shall recursively descend the directory hierarchy from each file specified by path, evaluating a Boolean expression composed of the primaries...
fold
The fold utility is a filter that shall fold lines from its input files, breaking the lines to have a maximum of width column positions (or bytes, if the -b...
fort77
The fort77 utility is the interface to the FORTRAN compilation system; it shall accept the full FORTRAN-77 language defined by the ANSI X3.9‐1978 standard. The...
fuser
The fuser utility shall write to standard output the process IDs of processes running on the local system that have one or more named files open. For block...
gencat
The gencat utility shall merge the message text source file msgfile into a formatted message catalog catfile. The file catfile shall be created if it does not...
getconf
In the first synopsis form, the getconf utility shall write to the standard output the value of the variable specified by the system_var operand. In the second...
getopts
The getopts utility shall retrieve options and option-arguments from a list of parameters. It shall support the Utility Syntax Guidelines 3 to 10, inclusive...
grep
The grep utility shall search the input files, selecting lines matching one or more patterns; the types of patterns are controlled by the options specified. The...
hash
The hash utility shall affect the way the current shell environment remembers the locations of utilities found as described in Section 2.9.1.1, Command Search...
head
The head utility shall copy its input files to the standard output, ending the output for each file at a designated point. Copying shall end at the point in...
iconv
The iconv utility shall convert the encoding of characters in file from one codeset to another and write the results to standard output. When the options...
id
If no user operand is provided, the id utility shall write the user and group IDs and the corresponding user and group names of the invoking process to standard...
ipcrm
The ipcrm utility shall remove zero or more message queues, semaphore sets, or shared memory segments. The interprocess communication facilities to be removed...
ipcs
The ipcs utility shall write information about active interprocess communication facilities. Without options, information shall be written in short format for...
jobs
The jobs utility shall display the status of jobs that were started in the current shell environment; see Section 2.12, Shell Execution Environment. When jobs...
join
The join utility shall perform an equality join on the files file1 and file2. The joined files shall be written to the standard output. The join field is a...
kill
The kill utility shall send a signal to the process or processes specified by each pid operand.
lex
The lex utility shall generate C programs to be used in lexical processing of character input, and that can be used as an interface to yacc. The C programs...
link
call link() function
ln
In the first synopsis form, the ln utility shall create a new directory entry (link) at the destination path specified by the target_file operand. If the -s...
locale
The locale utility shall write information about the current locale environment, or all public locales, to the standard output. For the purposes of this...
localedef
The localedef utility shall convert source definitions for locale categories into a format usable by the functions and utilities whose operational behavior is...
logger
The logger utility saves a message, in an unspecified manner and format, containing the string operands provided by the user. The messages are expected to be...
logname
The logname utility shall write the user's login name to standard output. The login name shall be the string that would be returned by the getlogin() function...
lp
The lp utility shall copy the input files to an output destination in an unspecified manner. The default output destination should be to a hardcopy device, such...
ls
For each operand that names a file of a type other than directory or symbolic link to a directory, ls shall write the name of the file as well as any requested...
m4
The m4 utility is a macro processor that shall read one or more text files, process them according to their included macro statements, and write the results to...
mailx
The mailx utility provides a message sending and receiving facility. It has two major modes, selected by the options used: Send Mode and Receive Mode. On...
make
The make utility shall update files that are derived from other files. A typical case is one where object files are derived from the corresponding source files...
man
The man utility shall write information about each of the name operands. If name is the name of a standard utility, man at a minimum shall write a message...
mesg
The mesg utility shall control whether other users are allowed to send messages via write, talk, or other utilities to a terminal device. The terminal device...
mkdir
The mkdir utility shall create the directories specified by the operands, in the order specified.
mkfifo
The mkfifo utility shall create the FIFO special files specified by the operands, in the order specified.
more
The more utility shall read files and either write them to the terminal on a page-by-page basis or filter them to standard output. If standard output is not a...
mv
In the first synopsis form, the mv utility shall move the file named by the source_file operand to the destination specified by the target_file. This first...
newgrp
The newgrp utility shall create a new shell execution environment with a new real and effective group identification. Of the attributes listed in Section 2.12...
nice
The nice utility shall invoke a utility, requesting that it be run with a different nice value (see the Base Definitions volume of POSIX.1‐2008, Section 3.240...
nl
The nl utility shall read lines from the named file or the standard input if no file is named and shall reproduce the lines to standard output. Lines shall be...
nm
The nm utility shall display symbolic information appearing in the object file, executable file, or object-file library named by file. If no symbolic...
nohup
The nohup utility shall invoke the utility named by the utility operand with arguments supplied as the argument operands. At the time the named utility is...
od
The od utility shall write the contents of its input files to standard output in a user-specified format.
paste
The paste utility shall concatenate the corresponding lines of the given input files, and write the resulting lines to standard output. The default operation of...
patch
The patch utility shall read a source (patch) file containing any of four forms of difference (diff) listings produced by the diff utility (normal, copied...
pathchk
The pathchk utility shall check that one or more pathnames are valid (that is, they could be used to access or create a file without causing syntax errors) and...
pax
The pax utility shall read, write, and write lists of the members of archive files and copy directory hierarchies. A variety of archive formats shall be...
pr
The pr utility is a printing and pagination filter. If multiple input files are specified, each shall be read, formatted, and written to standard output.
printf
The printf utility shall write formatted operands to the standard output. The argument operands shall be formatted under control of the format operand.
ps
The ps utility shall write information about processes, subject to having appropriate privileges to obtain information about those processes. By default, ps...
pwd
The pwd utility shall write to standard output an absolute pathname of the current working directory, which does not contain the filenames dot or dot-dot.
qalter
The attributes of a batch job are altered by a request to the batch server that manages the batch job. The qalter utility is a user-accessible batch client that...
qdel
A batch job is deleted by sending a request to the batch server that manages the batch job. A batch job that has been deleted is no longer subject to management...
qhold
A hold is placed on a batch job by a request to the batch server that manages the batch job. A batch job that has one or more holds is not eligible for...
qmove
To move a batch job is to remove the batch job from the batch queue in which it resides and instantiate the batch job in another batch queue. A batch job is...
qmsg
To send a message to a batch job is to request that a server write a message string into one or more output files of the batch job. A message is sent to a batch...
qrerun
To rerun a batch job is to terminate the session leader of the batch job, delete any associated checkpoint files, and return the batch job to the batch queued...
qrls
A batch job might have one or more holds, which prevent the batch job from executing. A batch job from which all the holds have been removed becomes eligible...
qselect
To select a set of batch jobs is to return the batch job_identifiers for each batch job that meets a list of selection criteria. A set of batch jobs is selected...
qsig
To signal a batch job is to send a signal to the session leader of the batch job. A batch job is signaled by sending a request to the batch server that manages...
qstat
The status of a batch job, batch queue, or batch server is obtained by a request to the server. The qstat utility is a user-accessible batch client that...
qsub
To submit a script is to create a batch job that executes the script. A script is submitted by a request to a batch server. The qsub utility is a...
read
The read utility shall read a single line from standard input. By default, unless the -r option is specified, <backslash> shall act as an escape character. An...
readonly
The variables whose names are specified shall be given the readonly attribute. The values of variables with the readonly attribute cannot be changed by...
renice
The renice utility shall request that the nice values (see the Base Definitions volume of POSIX.1‐2008, Section 3.240, Nice Value) of one or more running...
return
The return utility shall cause the shell to stop executing the current function or dot script. If the shell is not currently executing a function or dot script...
rm
The rm utility shall remove the directory entry specified by each file argument. If either of the files dot or dot-dot are specified as the basename portion of...
rmdir
The rmdir utility shall remove the directory entry specified by each dir operand. For each dir operand, the rmdir utility shall perform actions equivalent to...
sed
The sed utility is a stream editor that shall read one or more text files, make editing changes according to a script of editing commands, and write the results...
set
If no options or arguments are specified, set shall write the names and values of all shell variables in the collation sequence of the current locale.
sh
The sh utility is a command language interpreter that shall execute commands read from a command line string, the standard input, or a specified file. The...
shift
The positional parameters shall be shifted. Positional parameter 1 shall be assigned the value of parameter (1+n), parameter 2 shall be assigned the value of...
sleep
The sleep utility shall suspend execution for at least the integral number of seconds specified by the time operand.
sort
sort, merge, or sequence check text files
split
The split utility shall read an input file and write one or more output files. The default size of each output file shall be 1000 lines. The size of the output...
strings
The strings utility shall look for printable strings in regular files and shall write those strings to standard output. A printable string is any sequence of...
strip
A strippable file is defined as a relocatable, object, or executable file. On XSI-conformant systems, a strippable file can also be an archive of object or...
stty
The stty utility shall set or report on terminal I/O characteristics for the device that is its standard input. Without options or operands specified, it shall...
tabs
The tabs utility shall display a series of characters that first clears the hardware terminal tab settings and then initializes the tab stops at the specified...
tail
The tail utility shall copy its input file to the standard output beginning at a designated place. Copying shall begin at the point in the file indicated by the...
talk
The talk utility is a two-way, screen-oriented communication program.
tee
The tee utility shall copy standard input to standard output, making a copy in zero or more files. The tee utility shall not buffer output. If the -a option is...
test
The test utility shall evaluate the expression and indicate the result of the evaluation by its exit status. An exit status of zero indicates that the...
time
The time utility shall invoke the utility named by the utility operand with arguments supplied as the argument operands and write a message to standard error...
times
write process times
touch
The touch utility shall change the last data modification timestamps, the last data access timestamps, or both. The time used can be specified by the -t time...
tput
The tput utility shall display terminal-dependent information. The manner in which this information is retrieved is unspecified. The information displayed shall...
tr
The tr utility shall copy the standard input to the standard output with substitution or deletion of selected characters. The options specified and the string1...
trap
If the first operand is an unsigned decimal integer, the shell shall treat all operands as conditions, and shall reset each condition to the default value...
true
The true utility shall return with exit code zero.
tsort
The tsort utility shall write to standard output a totally ordered list of items consistent with a partial ordering of items contained in the input. The...
tty
The tty utility shall write to the standard output the name of the terminal that is open as standard input. The name that is used shall be equivalent to the...
type
The type utility shall indicate how each argument would be interpreted if used as a command name.
ulimit
The ulimit utility shall set or report the file-size writing limit imposed on files written by the shell and its child processes (files of any size may be...
umask
The umask utility shall set the file mode creation mask of the current shell execution environment (see Section 2.12, Shell Execution Environment) to the value...
unalias
The unalias utility shall remove the definition for each alias name specified. See Section 2.3.1, Alias Substitution. The aliases shall be removed from the...
uname
By default, the uname utility shall write the operating system name to standard output. When options are specified, symbols representing one or more system...
uncompress
The uncompress utility shall restore files to their original state after they have been compressed using the compress utility. If no files are specified, the...
unexpand
The unexpand utility shall copy files or standard input to standard output, converting <blank> characters at the beginning of each line into the maximum number...
uniq
The uniq utility shall read an input file comparing adjacent lines, and write one copy of each input line on the output. The second and succeeding copies of...
unlink
call the unlink() function
unset
Each variable or function specified by name shall be unset. If -v is specified, name refers to a variable name and the shell shall unset it and remove it from...
uucp
The uucp utility shall copy files named by the source-file argument to the destination-file argument. The files named can be on local or remote systems. The...
uudecode
The uudecode utility shall read a file, or standard input if no file is specified, that includes data created by the uuencode utility. The uudecode utility...
uuencode
The uuencode utility shall write an encoded version of the named input file, or standard input if no file is specified, to standard output. The output shall be...
uustat
The uustat utility shall display the status of, or cancel, previously specified uucp requests, or provide general status on uucp connections to other systems...
uux
The uux utility shall gather zero or more files from various systems, execute a shell pipeline (see Section 2.9, Shell Commands) on a specified system, and then...
vi
This utility shall be provided on systems that both support the User Portability Utilities option and define the POSIX2_CHAR_TERM symbol. On other systems it is...
wait
When an asynchronous list (see Section 2.9.3.1, Examples) is started by the shell, the process ID of the last command in each element of the asynchronous list...
wc
The wc utility shall read one or more input files and, by default, write the number of <newline> characters, words, and bytes contained in each input file to...
who
The who utility shall list various pieces of information about accessible users. The domain of accessibility is implementation-defined. Based on the options...
write
The write utility shall read lines from the standard input and write them to the terminal of the specified user.
xargs
The xargs utility shall construct a command line consisting of the utility and argument operands specified followed by as many arguments read in sequence from...
yacc
The yacc utility shall read a description of a context-free grammar in grammar and write C source code, conforming to the ISO C standard, to a code file, and...
zcat
The zcat utility shall write to standard output the uncompressed form of files that have been compressed using the compress utility. It is the equivalent of...
System Calls (Section 2)
accept
The accept() system call is used with connection-based socket types (SOCK_STREAM, SOCK_SEQPACKET). It extracts the first connection request on the queue of...
access
access() checks whether the calling process can access the file pathname. If pathname is a symbolic link, it is dereferenced. The mode specifies the...
acct
The acct() system call enables or disables process accounting. If called with the name of an existing file as its argument, accounting is turned on, and records...
add_key
add_key() asks the kernel to create or update a key of the given type and description, instantiate it with the payload of length plen, and to attach it to the...
adjtimex
Linux uses David L. Mills' clock adjustment algorithm (see RFC 5905). The system call adjtimex() reads and optionally sets adjustment parameters for this...
alarm
alarm() arranges for a SIGALRM signal to be delivered to the calling process in seconds seconds. If seconds is zero, any pending alarm is canceled. In any event...
alloc_hugepages
The system calls alloc_hugepages() and free_hugepages() were introduced in Linux 2.5.36 and removed again in 2.5.54. They existed only on i386 and ia64 (when...
arch_prctl
The arch_prctl() function sets architecture-specific process or thread state. code selects a subfunction and passes argument addr to it; addr is interpreted as...
bdflush
Note: Since Linux 2.6, this system call is deprecated and does nothing. It is likely to disappear altogether in a future kernel release. Nowadays, the task...
bind
When a socket is created with socket(2), it exists in a name space (address family) but has no address assigned to it. bind() assigns the address specified by...
bpf
The bpf() system call performs a range of operations related to extended Berkeley Packet Filters. Extended BPF (or eBPF) is similar to the original ("classic")...
brk
brk() and sbrk() change the location of the program break, which defines the end of the process's data segment (i.e., the program break is the first location...
cacheflush
cacheflush() flushes the contents of the indicated cache(s) for the user addresses in the range addr to (addr+nbytes-1).
capget
As of Linux 2.2, the power of the superuser (root) has been partitioned into a set of discrete capabilities. Each thread has a set of effective capabilities...
chdir
chdir() changes the current working directory of the calling process to the directory specified in path. fchdir() is identical to chdir(); the only difference...
chmod
The chmod() and fchmod() system calls change a files mode bits. (The file mode consists of the file permission bits plus the set-user-ID, set-group-ID, and...
chown
These system calls change the owner and group of a file.
chroot
chroot() changes the root directory of the calling process to that specified in path. This directory will be used for pathnames beginning with /. The root...
clock_getres
The function clock_getres() finds the resolution (precision) of the specified clock clk_id, and, if res is non-NULL, stores it in the struct timespec pointed to...
clock_nanosleep
Like nanosleep(2), clock_nanosleep() allows the calling thread to sleep for an interval specified with nanosecond precision. It differs in allowing the caller...
clone
clone() creates a new process, in a manner similar to fork(2). This page describes both the glibc clone() wrapper function and the underlying system call on...
close
close() closes a file descriptor, so that it no longer refers to any file and may be reused. Any record locks (see fcntl(2)) held on the file it was associated...
connect
The connect() system call connects the socket referred to by the file descriptor sockfd to the address specified by addr. The addrlen argument specifies the...
copy_file_range
The copy_file_range() system call performs an in-kernel copy between two file descriptors without the additional cost of transferring data from the kernel to...
create_module
Note: This system call is present only in kernels before Linux 2.6. create_module() attempts to create a loadable module entry and reserve the kernel memory...
delete_module
The delete_module() system call attempts to remove the unused loadable module entry identified by name. If the module has an exit function, then that function...
dup
The dup() system call creates a copy of the file descriptor oldfd, using the lowest-numbered unused file descriptor for the new descriptor. After a successful...
epoll_create
epoll_create() creates an epoll(7) instance. Since Linux 2.6.8, the size argument is ignored, but must be greater than zero; see Notes below. epoll_create()...
epoll_ctl
This system call performs control operations on the epoll(7) instance referred to by the file descriptor epfd. It requests that the operation op be performed...
epoll_wait
The epoll_wait() system call waits for events on the epoll(7) instance referred to by the file descriptor epfd. The memory area pointed to by events will...
eventfd
eventfd() creates an "eventfd object" that can be used as an event wait/notify mechanism by user-space applications, and by the kernel to notify user-space...
execve
execve() executes the program pointed to by filename.
execveat
The execveat() system call executes the program referred to by the combination of dirfd and pathname. It operates in exactly the same way as execve(2), except...
_exit
The function _exit() terminates the calling process "immediately". Any open file descriptors belonging to the process are closed; any children of the process...
exit_group
This system call is equivalent to exit(2) except that it terminates not only the calling thread, but all threads in the calling process's thread group.
fallocate
This is a nonportable, Linux-specific system call. For the portable, POSIX.1-specified method of ensuring that space is allocated for a file, see...
fanotify_init
For an overview of the fanotify API, see fanotify(7). fanotify_init() initializes a new fanotify group and returns a file descriptor for the event queue...
fanotify_mark
For an overview of the fanotify API, see fanotify(7). fanotify_mark() adds, removes, or modifies an fanotify mark on a filesystem object. The caller must have...
fcntl
fcntl() performs one of the operations described below on the open file descriptor fd. The operation is determined by cmd. fcntl() can take an optional third...
flock
Apply or remove an advisory lock on the open file specified by fd.
fork
fork() creates a new process by duplicating the calling process. The new process is referred to as the child process. The calling process is referred to as the...
fsync
fsync() transfers ("flushes") all modified in-core data of (i.e., modified buffer cache pages for) the file referred to by the file descriptor fd to the disk...
futex
The futex() system call provides a method for waiting until a certain condition becomes true. It is typically used as a blocking construct in the context of...
futimesat
This system call is obsolete. Use utimensat(2) instead. The futimesat() system call operates in exactly the same way as utimes(2), except for the differences...
getcpu
The getcpu() system call identifies the processor and node on which the calling thread or process is currently running and writes them into the integers pointed...
getdents
These are not the interfaces you are interested in. Look at readdir(3) for the POSIX-conforming C library interface. This page documents the bare kernel system...
getdomainname
These functions are used to access or to change the NIS domain name of the host system. setdomainname() sets the domain name to the value given in the character...
getgid
getgid() returns the real group ID of the calling process. getegid() returns the effective group ID of the calling process.
getgroups
getgroups() returns the supplementary group IDs of the calling process in list. The argument size should be set to the maximum number of items that can be...
gethostname
These system calls are used to access or to change the hostname of the current processor. sethostname() sets the hostname to the value given in the character...
getitimer
These system calls provide access to interval timers, that is, timers that initially expire at some point in the future, and (optionally) at regular intervals...
get_kernel_syms
Note: This system call is present only in kernels before Linux 2.6. If table is NULL, get_kernel_syms() returns the number of symbols available for query.
get_mempolicy
get_mempolicy() retrieves the NUMA policy of the calling thread or of a memory address, depending on the setting of flags. A NUMA machine has different memory...
getpagesize
The function getpagesize() returns the number of bytes in a memory page, where "page" is a fixed-length block, the unit for memory allocation and file mapping...
getpeername
getpeername() returns the address of the peer connected to the socket sockfd, in the buffer pointed to by addr. The addrlen argument should be initialized to...
getpid
getpid() returns the process ID of the calling process. (This is often used by routines that generate unique temporary filenames.) getppid() returns the process...
getpriority
The scheduling priority of the process, process group, or user, as indicated by which and who is obtained with the getpriority() call and set with the...
getrandom
The getrandom() system call fills the buffer pointed to by buf with up to buflen random bytes. These bytes can be used to seed user-space random number...
getresuid
getresuid() returns the real UID, the effective UID, and the saved set-user-ID of the calling process, in the arguments ruid, euid, and suid, respectively...
getrlimit
The getrlimit() and setrlimit() system calls get and set resource limits respectively.
get_robust_list
The robust futex implementation needs to maintain per-thread lists of the robust futexes which are to be unlocked when the thread exits. These lists are managed...
getrusage
get resource usage
getsid
getsid(0) returns the session ID of the calling process. getsid() returns the session ID of the process with process ID pid. If pid is 0, getsid() returns the...
getsockname
getsockname() returns the current address to which the socket sockfd is bound, in the buffer pointed to by addr. The addrlen argument should be initialized to...
getsockopt
getsockopt() and setsockopt() manipulate options for the socket referred to by the file descriptor sockfd. Options may exist at multiple protocol levels; they...
gettid
gettid() returns the caller's thread ID (TID). In a single-threaded process, the thread ID is equal to the process ID (PID, as returned by getpid(2)). In a...
gettimeofday
The functions gettimeofday() and settimeofday() can get and set the time as well as a timezone.
getuid
getuid() returns the real user ID of the calling process. geteuid() returns the effective user ID of the calling process.
getunwind
Note: this function is obsolete. The IA-64-specific getunwind() system call copies the kernel's call frame unwind data into the buffer pointed to by buf and...
getxattr
Extended attributes are name:value pairs associated with inodes (files, directories, symbolic links, etc.). They are extensions to the normal attributes which...
idle
idle() is an internal system call used during bootstrap. It marks the process's pages as swappable, lowers its priority, and enters the main scheduling loop...
init_module
init_module() loads an ELF image into kernel space, performs any necessary symbol relocations, initializes module parameters to values provided by the caller...
inotify_add_watch
inotify_add_watch() adds a new watch, or modifies an existing watch, for the file whose location is specified in pathname; the caller must have read permission...
inotify_init
For an overview of the inotify API, see inotify(7). inotify_init() initializes a new inotify instance and returns a file descriptor associated with a new...
inotify_rm_watch
inotify_rm_watch() removes the watch associated with the watch descriptor wd from the inotify instance associated with the file descriptor fd. Removing a watch...
intro
Section 2 of the manual describes the Linux system calls. A system call is an entry point into the Linux kernel. Usually, system calls are not invoked directly...
io_cancel
The io_cancel() system call attempts to cancel an asynchronous I/O operation previously submitted with io_submit(2). The iocb argument describes the operation...
ioctl
The ioctl() function manipulates the underlying device parameters of special files. In particular, many operating characteristics of character special files...
ioctl_fat
The ioctl(2) system call can be used to read and write metadata of FAT filesystems that are not accessible using other system calls.Reading and setting file...
ioctl_ficlonerange
If a filesystem supports files sharing physical storage between multiple files ("reflink"), this ioctl(2) operation can be used to make some of the data in the...
ioctl_fideduperange
If a filesystem supports files sharing physical storage between multiple files, this ioctl(2) operation can be used to make some of the data in the src_fd file...
ioctl_list
This is Ioctl List 1.3.27, a list of ioctl calls in Linux/i386 kernel 1.3.27. It contains 421 ioctls from </usr/include/{asm,linux}/*.h>. For each ioctl, its...
io_destroy
The io_destroy() system call will attempt to cancel all outstanding asynchronous I/O operations against ctx_id, will block on the completion of all operations...
io_getevents
The io_getevents() system call attempts to read at least min_nr events and up to nr events from the completion queue of the AIO context specified by ctx_id.
ioperm
ioperm() sets the port access permission bits for the calling thread for num bits starting from port address from. If turn_on is nonzero, then permission for...
iopl
iopl() changes the I/O privilege level of the calling process, as specified by the two least significant bits in level. This call is necessary to allow...
ioprio_set
The ioprio_get() and ioprio_set() system calls respectively get and set the I/O scheduling class and priority of one or more threads. The which and who...
io_setup
The io_setup() system call creates an asynchronous I/O context suitable for concurrently processing nr_events operations. The ctx_idp argument must not point to...
io_submit
The io_submit() system call queues nr I/O request blocks for processing in the AIO context ctx_id. The iocbpp argument should be an array of nr AIO control...
ipc
ipc() is a common kernel entry point for the System V IPC calls for messages, semaphores, and shared memory. call determines which IPC function to invoke; the...
kcmp
The kcmp() system call can be used to check whether the two processes identified by pid1 and pid2 share a kernel resource such as virtual memory, file...
kexec_load
The kexec_load() system call loads a new kernel that can be executed later by reboot(2). The flags argument is a bit mask that controls the operation of the...
keyctl
manipulate the kernel's key management facility
kill
The kill() system call can be used to send any signal to any process group or process. If pid is positive, then signal sig is sent to the process with the ID...
killpg
killpg() sends the signal sig to the process group pgrp. See signal(7) for a list of signals. If pgrp is 0, killpg() sends the signal to the calling process's...
link
link() creates a new link (also known as a hard link) to an existing file. If newpath exists, it will not be overwritten. This new name may be used exactly as...
listen
listen() marks the socket referred to by sockfd as a passive socket, that is, as a socket that will be used to accept incoming connection requests using...
listxattr
Extended attributes are name:value pairs associated with inodes (files, directories, symbolic links, etc.). They are extensions to the normal attributes which...
llseek
The _llseek() function repositions the offset of the open file description associated with the file descriptor fd to (offset_high<<32) | offset_low bytes...
lookup_dcookie
Look up the full path of the directory entry specified by the value cookie. The cookie is an opaque identifier uniquely identifying a particular directory...
lseek
reposition read/write file offset
madvise
The madvise() system call is used to give advice or directions to the kernel about the address range beginning at address addr and with size length bytes...
mbind
mbind() sets the NUMA memory policy, which consists of a policy mode and zero or more nodes, for the memory range starting with addr and continuing for len...
membarrier
The membarrier() system call helps reducing the overhead of the memory barrier instructions required to order memory accesses on multi-core systems. However...
memfd_create
memfd_create() creates an anonymous file and returns a file descriptor that refers to it. The file behaves like a regular file, and so can be modified...
migrate_pages
migrate_pages() attempts to move all pages of the process pid that are in memory nodes old_nodes to the memory nodes in new_nodes. Pages not located in any node...
mincore
mincore() returns a vector that indicates whether pages of the calling process's virtual memory are resident in core (RAM), and so will not cause a disk access...
mkdir
mkdir() attempts to create a directory named pathname. The argument mode specifies the mode for the new directory (see stat(2)). It is modified by the process's...
mknod
The system call mknod() creates a filesystem node (file, device special file, or named pipe) named pathname, with attributes specified by mode and dev. The mode...
mlock
mlock(), mlock2(), and mlockall() lock part or all of the calling process's virtual address space into RAM, preventing that memory from being paged to the swap...
mmap
mmap() creates a new mapping in the virtual address space of the calling process. The starting address for the new mapping is specified in addr. The length...
mmap2
This is probably not the system call that you are interested in; instead, see mmap(2), which describes the glibc wrapper function that invokes this system call...
modify_ldt
modify_ldt() reads or writes the local descriptor table (LDT) for a process. The LDT is an array of segment descriptors that can be referenced by user code...
mount
mount() attaches the filesystem specified by source (which is often a pathname referring to a device, but can also be the pathname of a directory or file, or a...
move_pages
move_pages() moves the specified pages of the process pid to the memory nodes specified by nodes. The result of the move is reflected in status. The flags...
mprotect
mprotect() changes protection for the calling process's memory page(s) containing any part of the address range in the interval [addr, addr+len-1]. addr must be...
mq_getsetattr
Do not use this system call. This is the low-level system call used to implement mq_getattr(3) and mq_setattr(3). For an explanation of how this system call...
mremap
mremap() expands (or shrinks) an existing memory mapping, potentially moving it at the same time (controlled by the flags argument and the available virtual...
msgctl
msgctl() performs the control operation specified by cmd on the System V message queue with identifier msqid.
msgget
The msgget() system call returns the System V message queue identifier associated with the value of the key argument. A new message queue is created if key has...
msgop
The msgsnd() and msgrcv() system calls are used, respectively, to send messages to, and receive messages from, a System V message queue. The calling process...
msync
msync() flushes changes made to the in-core copy of a file that was mapped into memory using mmap(2) back to the filesystem. Without use of this call, there is...
nanosleep
nanosleep() suspends the execution of the calling thread until either at least the time specified in *req has elapsed, or the delivery of a signal that triggers...
nfsservctl
Note: Since Linux 3.1, this system call no longer exists. It has been replaced by a set of files in the nfsd filesystem; see nfsd(7).
nice
nice() adds inc to the nice value for the calling process. (A higher nice value means a low priority.) Only the superuser may specify a negative increment, or...
open
Given a pathname for a file, open() returns a file descriptor, a small, nonnegative integer for use in subsequent system calls (read(2), write(2), lseek(2)...
open_by_handle_at
The name_to_handle_at() and open_by_handle_at() system calls split the functionality of openat(2) into two parts: name_to_handle_at() returns an opaque handle...
outb
This family of functions is used to do low-level port input and output. The out* functions do port output, the in* functions do port input; the b-suffix...
pause
pause() causes the calling process (or thread) to sleep until a signal is delivered that either terminates the process or causes the invocation of a...
perf_event_open
Given a list of parameters, perf_event_open() returns a file descriptor, for use in subsequent system calls (read(2), mmap(2), prctl(2), fcntl(2), etc.). A call...
perfmonctl
The IA-64-specific perfmonctl() system call provides an interface to the PMU (performance monitoring unit). The PMU consists of PMD (performance monitoring...
personality
Linux supports different execution domains, or personalities, for each process. Among other things, execution domains tell Linux how to map signal numbers into...
pipe
pipe() creates a pipe, a unidirectional data channel that can be used for interprocess communication. The array pipefd is used to return two file descriptors...
pivot_root
pivot_root() moves the root filesystem of the calling process to the directory put_old and makes new_root the new root filesystem of the calling process. The...
poll
poll() performs a similar task to select(2): it waits for one of a set of file descriptors to become ready to perform I/O.
posix_fadvise
Programs can use posix_fadvise() to announce an intention to access file data in a specific pattern in the future, thus allowing the kernel to perform...
prctl
prctl() is called with a first argument describing what to do (with values defined in <linux/prctl.h>), and further arguments with a significance depending on...
pread
pread() reads up to count bytes from file descriptor fd at offset offset (from the start of the file) into the buffer starting at buf. The file offset is not...
process_vm_readv
These system calls transfer data between the address space of the calling process ("the local process") and the process identified by pid ("the remote...
ptrace
The ptrace() system call provides a means by which one process (the "tracer") may observe and control the execution of another process (the "tracee"), and...
query_module
Note: This system call is present only in kernels before Linux 2.6. query_module() requests information from the kernel about loadable modules. The returned...
quotactl
The quota system can be used to set per-user, per-group, and per-project limits on the amount of disk space used on a filesystem. For each user and/or group, a...
read
read() attempts to read up to count bytes from file descriptor fd into the buffer starting at buf. On files that support seeking, the read operation commences...
readahead
readahead() initiates readahead on a file so that subsequent reads from that file will be satisfied from the cache, and not block on disk I/O (assuming the...
readdir
This is not the function you are interested in. Look at readdir(3) for the POSIX conforming C library interface. This page documents the bare kernel system call...
readlink
readlink() places the contents of the symbolic link pathname in the buffer buf, which has size bufsiz. readlink() does not append a null byte to buf. It will...
readv
The readv() system call reads iovcnt buffers from the file associated with the file descriptor fd into the buffers described by iov ("scatter input"). The...
reboot
The reboot() call reboots the system, or enables/disables the reboot keystroke (abbreviated CAD, since the default is Ctrl-Alt-Delete; it can be changed using...
recv
The recv(), recvfrom(), and recvmsg() calls are used to receive messages from a socket. They may be used to receive data on both connectionless and...
recvmmsg
The recvmmsg() system call is an extension of recvmsg(2) that allows the caller to receive multiple messages from a socket using a single system call. (This has...
remap_file_pages
Note: this system call is (since Linux 3.16) deprecated and will eventually be replaced by a slower in-kernel emulation. Those few applications that use this...
removexattr
Extended attributes are name:value pairs associated with inodes (files, directories, symbolic links, etc.). They are extensions to the normal attributes which...
rename
rename() renames a file, moving it between directories if required. Any other hard links to the file (as created using link(2)) are unaffected. Open file...
request_key
request_key() asks the kernel to find a key of the given type that matches the specified description and, if successful, to attach it to the nominated keyring...
restart_syscall
The restart_syscall() system call is used to restart certain system calls after a process that was stopped by a signal (e.g., SIGSTOP or SIGTSTP) is later...
rmdir
rmdir() deletes a directory, which must be empty.
rtas
ppc_rtas enables userspace manipulation of the RunTime Abstraction Services (RTAS). RTAS provides for a portable method of access and setting system...
rt_sigqueueinfo
The rt_sigqueueinfo() and rt_tgsigqueueinfo() system calls are the low-level interfaces used to send a signal plus data to a process or thread. The receiver of...
s390_pci_mmio_write
The s390_pci_mmio_write() system call writes length bytes of data from the user-space buffer user_buffer to the PCI MMIO memory location specified by mmio_addr...
s390_runtime_instr
The s390_runtime_instr() system call starts or stops CPU run-time instrumentation for the calling thread. The command argument controls whether run-time...
sched_get_priority_max
sched_get_priority_max() returns the maximum priority value that can be used with the scheduling algorithm identified by policy. sched_get_priority_min()...
sched_rr_get_interval
sched_rr_get_interval() writes into the timespec structure pointed to by tp the round-robin time quantum for the process identified by pid. The specified...
sched_setaffinity
A thread's CPU affinity mask determines the set of CPUs on which it is eligible to run. On a multiprocessor system, setting the CPU affinity mask can be used to...
sched_setattr
sched_setattr() The sched_setattr() system call sets the scheduling policy and associated attributes for the thread whose ID is specified in pid. If pid equals...
sched_setparam
sched_setparam() sets the scheduling parameters associated with the scheduling policy for the process identified by pid. If pid is zero, then the parameters of...
sched_setscheduler
The sched_setscheduler() system call sets both the scheduling policy and parameters for the thread whose ID is specified in pid. If pid equals zero, the...
sched_yield
sched_yield() causes the calling thread to relinquish the CPU. The thread is moved to the end of the queue for its static priority and a new thread gets to run.
seccomp
The seccomp() system call operates on the Secure Computing (seccomp) state of the calling process.
select
select() and pselect() allow a program to monitor multiple file descriptors, waiting until one or more of the file descriptors become "ready" for some class of...
select_tut
select() (or pselect()) is used to efficiently monitor multiple file descriptors, to see if any of them is, or becomes, "ready"; that is, to see whether I/O...
semctl
semctl() performs the control operation specified by cmd on the System V semaphore set identified by semid, or on the semnum-th semaphore of that set. (The...
semget
The semget() system call returns the System V semaphore set identifier associated with the argument key. A new set of nsems semaphores is created if key has the...
semop
System V semaphore operations
send
The system calls send(), sendto(), and sendmsg() are used to transmit a message to another socket. The send() call may be used only when the socket is in a...
sendfile
sendfile() copies data between one file descriptor and another. Because this copying is done within the kernel, sendfile() is more efficient than the...
sendmmsg
The sendmmsg() system call is an extension of sendmsg(2) that allows the caller to transmit multiple messages on a socket using a single system call. (This has...
seteuid
seteuid() sets the effective user ID of the calling process. Unprivileged processes may only set the effective user ID to the real user ID, the effective user...
setfsgid
The system call setfsgid() changes the value of the caller's filesystem group ID—the group ID that the Linux kernel uses to check for all accesses to the...
setfsuid
The system call setfsuid() changes the value of the caller's filesystem user ID—the user ID that the Linux kernel uses to check for all accesses to the...
setgid
setgid() sets the effective group ID of the calling process. If the calling process is privileged (has the CAP_SETGID capability in its user namespace), the...
set_mempolicy
set_mempolicy() sets the NUMA memory policy of the calling thread, which consists of a policy mode and zero or more nodes, to the values specified by the mode...
setns
Given a file descriptor referring to a namespace, reassociate the calling thread with that namespace. The fd argument is a file descriptor referring to one of...
setpgid
All of these interfaces are available on Linux, and are used for getting and setting the process group ID (PGID) of a process. The preferred, POSIX.1-specified...
setresuid
setresuid() sets the real user ID, the effective user ID, and the saved set-user-ID of the calling process. An unprivileged process may change its real UID...
setreuid
setreuid() sets real and effective user IDs of the calling process. Supplying a value of -1 for either the real or effective user ID forces the system to leave...
setsid
setsid() creates a new session if the calling process is not a process group leader. The calling process is the leader of the new session (i.e., its session ID...
set_thread_area
Linux dedicates three global descriptor table (GDT) entries for thread-local storage. For more information about the GDT, see the Intel Software Developer's...
set_tid_address
For each thread, the kernel maintains two attributes (addresses) called set_child_tid and clear_child_tid. These two attributes contain the value NULL by...
setuid
setuid() sets the effective user ID of the calling process. If the calling process is privileged (more precisely: if the process has the CAP_SETUID capability...
setup
setup() is called once from within linux/init/main.c. It calls initialization functions for devices and filesystems configured into the kernel and then mounts...
setxattr
Extended attributes are name:value pairs associated with inodes (files, directories, symbolic links, etc.). They are extensions to the normal attributes which...
sgetmask
These system calls are obsolete. Do not use them; use sigprocmask(2) instead. sgetmask() returns the signal mask of the calling process. ssetmask() sets the...
shmctl
shmctl() performs the control operation specified by cmd on the System V shared memory segment whose identifier is given in shmid.
shmget
shmget() returns the identifier of the System V shared memory segment associated with the value of the argument key. A new shared memory segment, with size...
shmop
shmat() shmat() attaches the System V shared memory segment identified by shmid to the address space of the calling process. The attaching address is specified...
shutdown
The shutdown() call causes all or part of a full-duplex connection on the socket associated with sockfd to be shut down. If how is SHUT_RD, further receptions...
sigaction
The sigaction() system call is used to change the action taken by a process on receipt of a specific signal. (See signal(7) for an overview of signals.) signum...
sigaltstack
sigaltstack() allows a process to define a new alternate signal stack and/or retrieve the state of an existing alternate signal stack. An alternate signal stack...
signal
The behavior of signal() varies across UNIX versions, and has also varied historically across different versions of Linux. Avoid its use: use sigaction(2)...
signalfd
signalfd() creates a file descriptor that can be used to accept signals targeted at the caller. This provides an alternative to the use of a signal handler or...
sigpending
sigpending() returns the set of signals that are pending for delivery to the calling thread (i.e., the signals which have been raised while blocked). The mask...
sigprocmask
sigprocmask() is used to fetch and/or change the signal mask of the calling thread. The signal mask is the set of signals whose delivery is currently blocked...
sigreturn
If the Linux kernel determines that an unblocked signal is pending for a process, then, at the next transition back to user mode in that process (e.g., upon...
sigsuspend
sigsuspend() temporarily replaces the signal mask of the calling process with the mask given by mask and then suspends the process until delivery of a signal...
sigwaitinfo
sigwaitinfo() suspends execution of the calling thread until one of the signals in set is pending (If one of the signals in set is already pending for the...
socket
socket() creates an endpoint for communication and returns a file descriptor that refers to that endpoint. The domain argument specifies a communication domain...
socketcall
socketcall() is a common kernel entry point for the socket system calls. call determines which socket function to invoke. args points to a block containing the...
socketpair
The socketpair() call creates an unnamed pair of connected sockets in the specified domain, of the specified type, and using the optionally specified protocol...
splice
splice() moves data between two file descriptors without copying between kernel address space and user address space. It transfers up to len bytes of data from...
spu_create
The spu_create() system call is used on PowerPC machines that implement the Cell Broadband Engine Architecture in order to access Synergistic Processor Units...
spu_run
The spu_run() system call is used on PowerPC machines that implement the Cell Broadband Engine Architecture in order to access Synergistic Processor Units...
stat
These functions return information about a file, in the buffer pointed to by buf. No permissions are required on the file itself, but—in the case of stat()...
statfs
The statfs() system call returns information about a mounted filesystem. path is the pathname of any file within the mounted filesystem.
stime
stime() sets the system's idea of the time and date. The time, pointed to by t, is measured in seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC). stime()...
subpage_prot
The PowerPC-specific subpage_prot() system call provides the facility to control the access permissions on individual 4kB subpages on systems configured with a...
swapcontext
swapcontext swaps out context old_ctx with new context new_ctx. The int r# values have no place in the system call functionality. The regs value indicates the...
swapon
swapon() sets the swap area to the file or block device specified by path. swapoff() stops swapping to the file or block device specified by path. If the...
symlink
symlink() creates a symbolic link named linkpath which contains the string target. Symbolic links are interpreted at run time as if the contents of the link had...
sync
sync() causes all pending modifications to file system metadata and cached file data to be written to the underlying filesystems. syncfs() is like sync(), but...
sync_file_range
sync_file_range() permits fine control when synchronizing the open file referred to by the file descriptor fd with disk. offset is the starting byte of the file...
syscall
syscall() is a small library function that invokes the system call whose assembly language interface has the specified number with the specified arguments...
_syscall
The important thing to know about a system call is its prototype. You need to know how many arguments, their types, and the function return type. There are...
syscalls
The system call is the fundamental interface between an application and the Linux kernel.System calls and library wrapper functions System calls are generally...
sysctl
Do not use this system call! See Notes. The _sysctl() call reads and/or writes kernel parameters. For example, the hostname, or the maximum number of open...
sysfs
sysfs() returns information about the filesystem types currently present in the kernel.
sysinfo
sysinfo() returns certain statistics on memory and swap usage, as well as the load average.
syslog
Note: Probably, you are looking for the C library function syslog(), which talks to syslogd(8); see syslog(3) for details. This page describes the kernel...
tee
tee() duplicates up to len bytes of data from the pipe referred to by the file descriptor fd_in to the pipe referred to by the file descriptor fd_out. It does...
time
time() returns the time as the number of seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC). If tloc is non-NULL, the return value is also stored in the...
timer_create
timer_create() creates a new per-process interval timer. The ID of the new timer is returned in the buffer pointed to by timerid, which must be a non-null...
timer_delete
timer_delete() deletes the timer whose ID is given in timerid. If the timer was armed at the time of this call, it is disarmed before being deleted. The...
timerfd_create
These system calls create and operate on a timer that delivers timer expiration notifications via a file descriptor. They provide an alternative to the use of...
timer_getoverrun
timer_getoverrun() returns the "overrun count" for the timer referred to by timerid. An application can use the overrun count to accurately calculate the number...
timer_settime
timer_settime() arms or disarms the timer identified by timerid. The new_value argument is pointer to an itimerspec structure that specifies the new initial...
times
times() stores the current process times in the struct tms that buf points to.
tkill
tgkill() sends the signal sig to the thread with the thread ID tid in the thread group tgid. (By contrast, kill(2) can be used to send a signal only to a...
truncate
The truncate() and ftruncate() functions cause the regular file named by path or referenced by fd to be truncated to a size of precisely length bytes. If the...
umask
umask() sets the calling process's file mode creation mask (umask) to mask & 0777 (i.e., only the file permission bits of mask are used), and returns the...
umount
umount() and umount2() remove the attachment of the (topmost) filesystem mounted on target. Appropriate privilege (Linux: the CAP_SYS_ADMIN capability) is...
uname
uname() returns system information in the structure pointed to by buf.
unimplemented
These system calls are not implemented in the Linux kernel.
unlink
unlink() deletes a name from the filesystem. If that name was the last link to a file and no processes have the file open, the file is deleted and the space it...
unshare
unshare() allows a process (or thread) to disassociate parts of its execution context that are currently being shared with other processes (or threads). Part of...
uselib
The system call uselib() serves to load a shared library to be used by the calling process. It is given a pathname. The address where to load is found in the...
ustat
ustat() returns information about a mounted filesystem. dev is a device number identifying a device containing a mounted filesystem.
utime
Note: modern applications may prefer to use the interfaces described in utimensat(2). The utime() system call changes the access and modification times of the...
utimensat
utimensat() and futimens() update the timestamps of a file with nanosecond precision. This contrasts with the historical utime(2) and utimes(2), which permit...
vfork
Standard description (From POSIX.1) The vfork() function has the same effect as fork(2), except that the behavior is undefined if the process created by vfork()...
vhangup
vhangup() simulates a hangup on the current terminal. This call arranges for other users to have a “clean” terminal at login time.
vm86
The system call vm86() was introduced in Linux 0.97p2. In Linux 2.1.15 and 2.0.28, it was renamed to vm86old(), and a new vm86() was introduced. The definition...
vmsplice
The vmsplice() system call maps nr_segs ranges of user memory described by iov into a pipe. The file descriptor fd must refer to a pipe.
wait
All of these system calls are used to wait for state changes in a child of the calling process, and obtain information about the child whose state has changed...
wait4
These functions are obsolete; use waitpid(2) or waitid(2) in new programs. The wait3() and wait4() system calls are similar to waitpid(2), but additionally...
write
write() writes up to count bytes from the buffer pointed buf to the file referred to by the file descriptor fd. The number of bytes written may be less than...
Library Functions (Section 3)
a64l
These functions provide a conversion between 32-bit long integers and little-endian base-64 ASCII strings (of length zero to six). If the string used as...
abort
The abort() first unblocks the SIGABRT signal, and then raises that signal for the calling process (as though raise(3) was called). This results in the abnormal...
abs
The abs() function computes the absolute value of the integer argument j. The labs(), llabs() and imaxabs() functions compute the absolute value of the argument...
acos
These functions calculate the arc cosine of x; that is the value whose cosine is x.
acosh
These functions calculate the inverse hyperbolic cosine of x; that is the value whose hyperbolic cosine is x.
addseverity
This function allows the introduction of new severity classes which can be addressed by the severity argument of the fmtmsg(3) function. By default, that...
adjtime
The adjtime() function gradually adjusts the system clock (as returned by gettimeofday(2)). The amount of time by which the clock is to be adjusted is specified...
aio_cancel
The aio_cancel() function attempts to cancel outstanding asynchronous I/O requests for the file descriptor fd. If aiocbp is NULL, all such requests are...
aio_error
The aio_error() function returns the error status for the asynchronous I/O request with control block pointed to by aiocbp. (See aio(7) for a description of the...
aio_fsync
The aio_fsync() function does a sync on all outstanding asynchronous I/O operations associated with aiocbp->aio_fildes. (See aio(7) for a description of the...
aio_init
The GNU-specific aio_init() function allows the caller to provide tuning hints to the glibc POSIX AIO implementation. Use of this function is optional, but to...
aio_read
The aio_read() function queues the I/O request described by the buffer pointed to by aiocbp. This function is the asynchronous analog of read(2). The arguments...
aio_return
The aio_return() function returns the final return status for the asynchronous I/O request with control block pointed to by aiocbp. (See aio(7) for a...
aio_suspend
wait for asynchronous I/O operation or timeout
aio_write
The aio_write() function queues the I/O request described by the buffer pointed to by aiocbp. This function is the asynchronous analog of write(2). The...
alloca
The alloca() function allocates size bytes of space in the stack frame of the caller. This temporary space is automatically freed when the function that called...
argz_add
These functions are glibc-specific. An argz vector is a pointer to a character buffer together with a length. The intended interpretation of the character...
asin
These functions calculate the principal value of the arc sine of x; that is the value whose sine is x.
asinh
These functions calculate the inverse hyperbolic sine of x; that is the value whose hyperbolic sine is x.
asprintf
The functions asprintf() and vasprintf() are analogs of sprintf(3) and vsprintf(3), except that they allocate a string large enough to hold the output including...
assert
This macro can help programmers find bugs in their programs, or handle exceptional cases via a crash that will produce limited debugging output. If expression...
assert_perror
If the macro NDEBUG was defined at the moment <assert.h> was last included, the macro assert_perror() generates no code, and hence does nothing at all...
atan
These functions calculate the principal value of the arc tangent of x; that is the value whose tangent is x.
atan2
These functions calculate the principal value of the arc tangent of y/x, using the signs of the two arguments to determine the quadrant of the result.
atanh
These functions calculate the inverse hyperbolic tangent of x; that is the value whose hyperbolic tangent is x.
atexit
The atexit() function registers the given function to be called at normal process termination, either via exit(3) or via return from the program's main()...
atof
The atof() function converts the initial portion of the string pointed to by nptr to double. The behavior is the same as strtod(nptr, NULL); except that atof()...
atoi
The atoi() function converts the initial portion of the string pointed to by nptr to int. The behavior is the same as strtol(nptr, NULL, 10); except that atoi()...
backtrace
backtrace() returns a backtrace for the calling program, in the array pointed to by buffer. A backtrace is the series of currently active function calls for the...
basename
Warning: there are two different functions basename() - see below. The functions dirname() and basename() break a null-terminated pathname string into directory...
bcmp
The bcmp() function compares the two byte sequences s1 and s2 of length n each. If they are equal, and in particular if n is zero, bcmp() returns 0. Otherwise...
bcopy
The bcopy() function copies n bytes from src to dest. The result is correct, even when both areas overlap.
bindresvport
bindresvport() is used to bind the socket referred to by the file descriptor sockfd to a privileged anonymous IP port, that is, a port number arbitrarily...
bsd_signal
The bsd_signal() function takes the same arguments, and performs the same task, as signal(2). The difference between the two is that bsd_signal() is guaranteed...
bsearch
The bsearch() function searches an array of nmemb objects, the initial member of which is pointed to by base, for a member that matches the object pointed to by...
bstring
The byte string functions perform operations on strings (byte arrays) that are not necessarily null-terminated. See the individual man pages for descriptions of...
bswap
These macros return a value in which the order of the bytes in their 2-, 4-, or 8-byte arguments is reversed.
btowc
The btowc() function converts c, interpreted as a multibyte sequence of length 1, starting in the initial shift state, to a wide character and returns it. If c...
byteorder
The htonl() function converts the unsigned integer hostlong from host byte order to network byte order. The htons() function converts the unsigned short integer...
bzero
The bzero() function sets the first n bytes of the area starting at s to zero (bytes containing '\0').
cabs
These functions return the absolute value of the complex number z. The result is a real number.
cacos
These functions calculate the complex arc cosine of z. If y = cacos(z), then z = ccos(y). The real part of y is chosen in the interval [0,pi].
cacosh
These functions calculate the complex arc hyperbolic cosine of z. If y = cacosh(z), then z = ccosh(y). The imaginary part of y is chosen in the interval...
canonicalize_file_name
The canonicalize_file_name() function returns a null-terminated string containing the canonicalized absolute pathname corresponding to path. In the returned...
carg
These functions calculate the complex argument (also called phase angle) of z, with a branch cut along the negative real axis. A complex number can be described...
casin
These functions calculate the complex arc sine of z. If y = casin(z), then z = csin(y). The real part of y is chosen in the interval [-pi/2,pi/2].
casinh
These functions calculate the complex arc hyperbolic sine of z. If y = casinh(z), then z = csinh(y). The imaginary part of y is chosen in the interval...
catan
These functions calculate the complex arc tangent of z. If y = catan(z), then z = ctan(y). The real part of y is chosen in the interval [-pi/2,pi/2].
catanh
These functions calculate the complex arc hyperbolic tangent of z. If y = catanh(z), then z = ctanh(y). The imaginary part of y is chosen in the interval...
catgets
catgets() reads the message message_number, in set set_number, from the message catalog identified by catalog, where catalog is a catalog descriptor returned...
catopen
The function catopen() opens a message catalog and returns a catalog descriptor. The descriptor remains valid until catclose() or execve(2). If a file...
cbrt
These functions return the (real) cube root of x. This function cannot fail; every representable real value has a representable real cube root.
ccos
These functions calculate the complex cosine of z.
ccosh
These functions calculate the complex hyperbolic cosine of z.
ceil
These functions return the smallest integral value that is not less than x. For example, ceil(0.5) is 1.0, and ceil(-0.5) is 0.0.
cexp
These functions calculate e (2.71828..., the base of natural logarithms) raised to the power of z.
cexp2
The function returns 2 raised to the power of z.
cfree
This function should never be used. Use free(3) instead.1-arg cfree In glibc, the function cfree() is a synonym for free(3), "added for compatibility with...
cimag
These functions return the imaginary part of the complex number z.
clearenv
The clearenv() function clears the environment of all name-value pairs and sets the value of the external variable environ to NULL. After this call, new...
clock
The clock() function returns an approximation of processor time used by the program.
clock_getcpuclockid
The clock_getcpuclockid() function obtains the ID of the CPU-time clock of the process whose ID is pid, and returns it in the location pointed to by clock_id...
clog
These functions calculate the complex natural logarithm of z, with a branch cut along the negative real axis. The logarithm clog() is the inverse function of...
clog10
The call clog10(z) is equivalent to: clog(z)/log(10) or equally: log10(cabs(c)) + I * carg(c) / log(10) The other functions perform the same task for float and...
clog2
The call clog2(z) is equivalent to clog(z)/log(2). The other functions perform the same task for float and long double. Note that z close to zero will cause an...
closedir
The closedir() function closes the directory stream associated with dirp. A successful call to closedir() also closes the underlying file descriptor associated...
cmsg
These macros are used to create and access control messages (also called ancillary data) that are not a part of the socket payload. This control information may...
confstr
confstr() gets the value of configuration-dependent string variables. The name argument is the system variable to be queried.
conj
These functions return the complex conjugate value of z. That is the value obtained by changing the sign of the imaginary part.
copysign
These functions return a value whose absolute value matches that of x, but whose sign bit matches that of y. For example, copysign(42.0, -1.0) and...
cos
These functions return the cosine of x, where x is given in radians.
cosh
hyperbolic cosine function
cpow
These functions calculate x raised to the power z (with a branch cut for x along the negative real axis.)
cproj
These functions project a point in the plane onto the surface of a Riemann Sphere, the one-point compactification of the complex plane. Each finite point z...
CPU_SET
The cpu_set_t data structure represents a set of CPUs. CPU sets are used by sched_setaffinity(2) and similar interfaces. The cpu_set_t data type is implemented...
creal
These functions return the real part of the complex number z.
crypt
crypt() is the password encryption function. It is based on the Data Encryption Standard algorithm with variations intended (among other things) to discourage...
csin
These functions calculate the complex sine of z.
csinh
These functions calculate the complex hyperbolic sine of z.
csqrt
These functions calculate the complex square root of z, with a branch cut along the negative real axis. (That means that csqrt(-1+eps*I) will be close to I...
ctan
These functions calculate the complex tangent of z.
ctanh
These functions calculate the complex hyperbolic tangent of z.
ctermid
ctermid() returns a string which is the pathname for the current controlling terminal for this process. If s is NULL, a static buffer is used, otherwise s...
ctime
The ctime(), gmtime() and localtime() functions all take an argument of data type time_t, which represents calendar time. When interpreted as an absolute time...
daemon
The daemon() function is for programs wishing to detach themselves from the controlling terminal and run in the background as system daemons. If nochdir is...
des_crypt
ecb_crypt() and cbc_crypt() implement the NBS DES (Data Encryption Standard). These routines are faster and more general purpose than crypt(3). They also are...
difftime
The difftime() function returns the number of seconds elapsed between time time1 and time time0, represented as a double. Each of the times is specified in...
dirfd
The function dirfd() returns the file descriptor associated with the directory stream dirp. This file descriptor is the one used internally by the directory...
div
The div() function computes the value numerator/denominator and returns the quotient and remainder in a structure named div_t that contains two integer members...
dladdr
The function dladdr() determines whether the address specified in addr is located in one of the shared objects loaded by the calling application. If it is, then...
dlerror
The dlerror() function returns a human-readable, null-terminated string describing the most recent error that occurred from a call to one of the functions in...
dlinfo
The dlinfo() function obtains information about the dynamically loaded object referred to by handle (typically obtained by an earlier call to dlopen(3) or...
dl_iterate_phdr
The dl_iterate_phdr() function allows an application to inquire at run time to find out which shared objects it has loaded. The dl_iterate_phdr() function walks...
dlopen
dlopen() The function dlopen() loads the dynamic shared object (shared library) file named by the null-terminated string filename and returns an opaque "handle"...
dlsym
The function dlsym() takes a "handle" of a dynamic loaded shared object returned by dlopen(3) along with a null-terminated symbol name, and returns the address...
drand48
These functions generate pseudo-random numbers using the linear congruential algorithm and 48-bit integer arithmetic. The drand48() and erand48() functions...
drand48_r
These functions are the reentrant analogs of the functions described in drand48(3). Instead of modifying the global random generator state, they use the...
duplocale
The duplocale() function creates a duplicate of the locale object referred to by locobj. If locobj is LC_GLOBAL_LOCALE, duplocale() creates a locale object...
dysize
The function returns 365 for a normal year and 366 for a leap year. The calculation for leap year is based on: (year) %4 == 0 && ((year) %100 != 0 || (year)...
ecvt
The ecvt() function converts number to a null-terminated string of ndigits digits (where ndigits is reduced to a system-specific limit determined by the...
ecvt_r
The functions ecvt_r(), fcvt_r(), qecvt_r(), and qfcvt_r() are identical to ecvt(3), fcvt(3), qecvt(3), and qfcvt(3), respectively, except that they do not...
encrypt
These functions encrypt and decrypt 64-bit messages. The setkey() function sets the key used by encrypt(). The key argument used here is an array of 64 bytes...
end
end of program segments
endian
These functions convert the byte encoding of integer values from the byte order that the current CPU (the "host") uses, to and from little-endian and big-endian...
envz_add
These functions are glibc-specific. An argz vector is a pointer to a character buffer together with a length, see argz_add(3). An envz vector is a special argz...
erf
These functions return the error function of x, defined as erf(x) = 2/sqrt(pi)* integral from 0 to x of exp(-t*t) dt
erfc
These functions return the complementary error function of x, that is, 1.0 - erf(x).
err
The err() and warn() family of functions display a formatted error message on the standard error output. In all cases, the last component of the program name, a...
errno
The <errno.h> header file defines the integer variable errno, which is set by system calls and some library functions in the event of an error to indicate what...
error
error() is a general error-reporting function. It flushes stdout, and then outputs to stderr the program name, a colon and a space, the message specified by the...
ether_aton
ether_aton() converts the 48-bit Ethernet host address asc from the standard hex-digits-and-colons notation into binary data in network byte order and returns a...
euidaccess
Like access(2), euidaccess() checks permissions and existence of the file identified by its argument pathname. However, whereas access(2) performs checks using...
exec
The exec() family of functions replaces the current process image with a new process image. The functions described in this manual page are front-ends for...
exit
The exit() function causes normal process termination and the value of status & 0377 is returned to the parent (see wait(2)). All functions registered with...
exp
These functions return the value of e (the base of natural logarithms) raised to the power of x.
exp10
These functions return the value of 10 raised to the power of x.
exp2
These functions return the value of 2 raised to the power of x.
expm1
These functions return a value equivalent to
fabs
These functions return the absolute value of the floating-point number x.
fclose
The fclose() function flushes the stream pointed to by stream (writing any buffered output data using fflush(3)) and closes the underlying file descriptor.
fcloseall
The fcloseall() function closes all of the calling process's open streams. Buffered output for each stream is written before it is closed (as for fflush(3))...
fdim
These functions return the positive difference, max(x-y,0), between their arguments.
fenv
These eleven functions were defined in C99, and describe the handling of floating-point rounding and exceptions (overflow, zero-divide, etc.).Exceptions The...
ferror
The function clearerr() clears the end-of-file and error indicators for the stream pointed to by stream. The function feof() tests the end-of-file indicator for...
fexecve
fexecve() performs the same task as execve(2), with the difference that the file to be executed is specified via a file descriptor, fd, rather than via a...
fflush
For output streams, fflush() forces a write of all user-space buffered data for the given output or update stream via the stream's underlying write function...
ffs
The ffs() function returns the position of the first (least significant) bit set in the word i. The least significant bit is position 1 and the most significant...
fgetc
fgetc() reads the next character from stream and returns it as an unsigned char cast to an int, or EOF on end of file or error. getc() is equivalent to fgetc()...
fgetgrent
The fgetgrent() function returns a pointer to a structure containing the group information from the file referred to by stream. The first time it is called it...
fgetpwent
The fgetpwent() function returns a pointer to a structure containing the broken out fields of a line in the file stream. The first time it is called it returns...
fgetwc
The fgetwc() function is the wide-character equivalent of the fgetc(3) function. It reads a wide character from stream and returns it. If the end of stream is...
fgetws
The fgetws() function is the wide-character equivalent of the fgets(3) function. It reads a string of at most n-1 wide characters into the wide-character array...
finite
The finite(), finitef(), and finitel() functions return a nonzero value if x is neither infinite nor a "not-a-number" (NaN) value, and 0 otherwise. The isnan()...
flockfile
The stdio functions are thread-safe. This is achieved by assigning to each FILE object a lockcount and (if the lockcount is nonzero) an owning thread. For each...
floor
These functions return the largest integral value that is not greater than x. For example, floor(0.5) is 0.0, and floor(-0.5) is -1.0.
fma
These functions compute x * y + z. The result is rounded as one ternary operation according to the current rounding mode (see fenv(3)).
fmax
These functions return the larger value of x and y.
fmemopen
The fmemopen() function opens a stream that permits the access specified by mode. The stream allows I/O to be performed on the string or memory buffer pointed...
fmin
These functions return the lesser value of x and y.
fmod
These functions compute the floating-point remainder of dividing x by y. The return value is x - n * y, where n is the quotient of x / y, rounded toward zero to...
fmtmsg
This function displays a message described by its arguments on the device(s) specified in the classification argument. For messages written to stderr, the...
fnmatch
The fnmatch() function checks whether the string argument matches the pattern argument, which is a shell wildcard pattern.
fopen
The fopen() function opens the file whose name is the string pointed to by path and associates a stream with it.
fopencookie
The fopencookie() function allows the programmer to create a custom implementation for a standard I/O stream. This implementation can store the stream's data at...
fpathconf
fpathconf() gets a value for the configuration option name for the open file descriptor fd. pathconf() gets a value for configuration option name for the...
fpclassify
Floating point numbers can have special values, such as infinite or NaN. With the macro fpclassify(x) you can find out what type x is. The macro takes any...
fpurge
The function fpurge() clears the buffers of the given stream. For output streams this discards any unwritten output. For input streams this discards any input...
fputwc
The fputwc() function is the wide-character equivalent of the fputc(3) function. It writes the wide character wc to stream. If ferror(stream) becomes true, it...
fputws
The fputws() function is the wide-character equivalent of the fputs(3) function. It writes the wide-character string starting at ws, up to but not including the...
fread
The function fread() reads nmemb items of data, each size bytes long, from the stream pointed to by stream, storing them at the location given by ptr. The...
frexp
These functions are used to split the number x into a normalized fraction and an exponent which is stored in exp.
fseek
The fseek() function sets the file position indicator for the stream pointed to by stream. The new position, measured in bytes, is obtained by adding offset...
fseeko
The fseeko() and ftello() functions are identical to fseek(3) and ftell(3) (see fseek(3)), respectively, except that the offset argument of fseeko() and the...
ftime
This function returns the current time as seconds and milliseconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
ftok
The ftok() function uses the identity of the file named by the given pathname (which must refer to an existing, accessible file) and the least significant 8...
fts
The fts functions are provided for traversing file hierarchies. A simple overview is that the fts_open() function returns a "handle" on a file hierarchy, which...
ftw
nftw() walks through the directory tree that is located under the directory dirpath, and calls fn() once for each entry in the tree. By default, directories are...
futimes
futimes() changes the access and modification times of a file in the same way as utimes(2), with the difference that the file whose timestamps are to be changed...
fwide
When mode is zero, the fwide() function determines the current orientation of stream. It returns a positive value if stream is wide-character oriented, that is...
gamma
These functions are deprecated: instead, use either the tgamma(3) or the lgamma(3) functions, as appropriate. For the definition of the Gamma function, see...
gcvt
The gcvt() function converts number to a minimal length null-terminated ASCII string and stores the result in buf. It produces ndigit significant digits in...
getaddrinfo
Given node and service, which identify an Internet host and a service, getaddrinfo() returns one or more addrinfo structures, each of which contains an Internet...
getaddrinfo_a
The getaddrinfo_a() function performs the same task as getaddrinfo(3), but allows multiple name look-ups to be performed asynchronously, with optional...
getauxval
The getauxval() function retrieves values from the auxiliary vector, a mechanism that the kernel's ELF binary loader uses to pass certain information to user...
getcontext
In a System V-like environment, one has the two types mcontext_t and ucontext_t defined in <ucontext.h> and the four functions getcontext(), setcontext()...
getcwd
These functions return a null-terminated string containing an absolute pathname that is the current working directory of the calling process. The pathname is...
getdate
The function getdate() converts a string representation of a date and time, contained in the buffer pointed to by string, into a broken-down time. The...
getdirentries
Read directory entries from the directory specified by fd into buf. At most nbytes are read. Reading starts at offset *basep, and *basep is updated with the new...
getdtablesize
getdtablesize() returns the maximum number of files a process can have open, one more than the largest possible value for a file descriptor.
getenv
The getenv() function searches the environment list to find the environment variable name, and returns a pointer to the corresponding value string. The...
getfsent
These functions read from the file /etc/fstab.
getgrent
The getgrent() function returns a pointer to a structure containing the broken-out fields of a record in the group database (e.g., the local group file...
getgrent_r
The functions getgrent_r() and fgetgrent_r() are the reentrant versions of getgrent(3) and fgetgrent(3). The former reads the next group entry from the stream...
getgrnam
The getgrnam() function returns a pointer to a structure containing the broken-out fields of the record in the group database (e.g., the local group file...
getgrouplist
The getgrouplist() function scans the group database (see group(5)) to obtain the list of groups that user belongs to. Up to *ngroups of these groups are...
gethostbyname
The gethostbyname*(), gethostbyaddr*(), herror(), and hstrerror() functions are obsolete. Applications should use getaddrinfo(3), getnameinfo(3), and...
gethostid
gethostid() and sethostid() respectively get or set a unique 32-bit identifier for the current machine. The 32-bit identifier is intended to be unique among all...
getifaddrs
The getifaddrs() function creates a linked list of structures describing the network interfaces of the local system, and stores the address of the first item of...
getipnodebyname
These functions are deprecated (and unavailable in glibc). Use getaddrinfo(3) and getnameinfo(3) instead. The getipnodebyname() and getipnodebyaddr() functions...
getline
getline() reads an entire line from stream, storing the address of the buffer containing the text into *lineptr. The buffer is null-terminated and includes the...
getloadavg
The getloadavg() function returns the number of processes in the system run queue averaged over various periods of time. Up to nelem samples are retrieved and...
getlogin
getlogin() returns a pointer to a string containing the name of the user logged in on the controlling terminal of the process, or a null pointer if this...
getmntent
These routines are used to access the filesystem description file /etc/fstab and the mounted filesystem description file /etc/mtab. The setmntent() function...
getnameinfo
The getnameinfo() function is the inverse of getaddrinfo(3): it converts a socket address to a corresponding host and service, in a protocol-independent manner...
getnetent
The getnetent() function reads the next entry from the networks database and returns a netent structure containing the broken-out fields from the entry. A...
getnetent_r
The getnetent_r(), getnetbyname_r(), and getnetbyaddr_r() functions are the reentrant equivalents of, respectively, getnetent(3), getnetbyname(3), and...
get_nprocs_conf
The function get_nprocs_conf() returns the number of processors configured by the operating system. The function get_nprocs() returns the number of processors...
getopt
The getopt() function parses the command-line arguments. Its arguments argc and argv are the argument count and array as passed to the main() function on...
getpass
This function is obsolete. Do not use it. If you want to read input without terminal echoing enabled, see the description of the ECHO flag in termios(3). The...
get_phys_pages
The function get_phys_pages() returns the total number of physical pages of memory available on the system. The function get_avphys_pages() returns the number...
getprotoent
The getprotoent() function reads the next entry from the protocols database (see protocols(5)) and returns a protoent structure containing the broken-out fields...
getprotoent_r
The getprotoent_r(), getprotobyname_r(), and getprotobynumber_r() functions are the reentrant equivalents of, respectively, getprotoent(3), getprotobyname(3)...
getpt
getpt() opens a pseudoterminal master and returns its file descriptor. It is equivalent to
getpw
The getpw() function reconstructs the password line entry for the given user ID uid in the buffer buf. The returned buffer contains a line of format
getpwent
The getpwent() function returns a pointer to a structure containing the broken-out fields of a record from the password database (e.g., the local password file...
getpwent_r
The functions getpwent_r() and fgetpwent_r() are the reentrant versions of getpwent(3) and fgetpwent(3). The former reads the next passwd entry from the stream...
getpwnam
The getpwnam() function returns a pointer to a structure containing the broken-out fields of the record in the password database (e.g., the local password file...
getrpcent
The getrpcent(), getrpcbyname(), and getrpcbynumber() functions each return a pointer to an object with the following structure containing the broken-out fields...
getrpcent_r
The getrpcent_r(), getrpcbyname_r(), and getrpcbynumber_r() functions are the reentrant equivalents of, respectively, getrpcent(3), getrpcbyname(3), and...
getrpcport
getrpcport() returns the port number for version versnum of the RPC program prognum running on host and using protocol proto. It returns 0 if it cannot contact...
gets
Never use this function. gets() reads a line from stdin into the buffer pointed to by s until either a terminating newline or EOF, which it replaces with a null...
getservent
The getservent() function reads the next entry from the services database (see services(5)) and returns a servent structure containing the broken-out fields...
getservent_r
The getservent_r(), getservbyname_r(), and getservbyport_r() functions are the reentrant equivalents of, respectively, getservent(3), getservbyname(3), and...
getspnam
Long ago it was considered safe to have encrypted passwords openly visible in the password file. When computers got faster and people got more...
getsubopt
getsubopt() parses the list of comma-separated suboptions provided in optionp. (Such a suboption list is typically produced when getopt(3) is used to parse a...
getttyent
These functions provide an interface to the file _PATH_TTYS (e.g., /etc/ttys). The function setttyent() opens the file or rewinds it if already open. The...
getumask
This function returns the current file creation mask. It is equivalent to
getusershell
The getusershell() function returns the next line from the file /etc/shells, opening the file if necessary. The line should contain the pathname of a valid user...
getutent
New applications should use the POSIX.1-specified "utmpx" versions of these functions; see Conforming to. utmpname() sets the name of the utmp-format file for...
getutmp
The getutmp() function copies the fields of the utmpx structure pointed to by ux to the corresponding fields of the utmp structure pointed to by u. The...
getw
getw() reads a word (that is, an int) from stream. It's provided for compatibility with SVr4. We recommend you use fread(3) instead. putw() writes the word w...
getwchar
The getwchar() function is the wide-character equivalent of the getchar(3) function. It reads a wide character from stdin and returns it. If the end of stream...
glob
The glob() function searches for all the pathnames matching pattern according to the rules used by the shell (see glob(7)). No tilde expansion or parameter...
gnu_get_libc_version
The function gnu_get_libc_version() returns a string that identifies the glibc version available on the system. The function gnu_get_libc_release() returns a...
grantpt
The grantpt() function changes the mode and owner of the slave pseudoterminal device corresponding to the master pseudoterminal referred to by fd. The user ID...
group_member
The group_member() function tests whether any of the caller's supplementary group IDs (as returned by getgroups(2)) matches gid.
gsignal
Don't use these functions under Linux. Due to a historical mistake, under Linux these functions are aliases for raise(3) and signal(2), respectively. Elsewhere...
hsearch
The three functions hcreate(), hsearch(), and hdestroy() allow the caller to create and manage a hash search table containing entries consisting of a key (a...
hypot
These functions return sqrt(x*x+y*y). This is the length of the hypotenuse of a right-angled triangle with sides of length x and y, or the distance of the point...
iconv
The iconv() function converts a sequence of characters in one character encoding to a sequence of characters in another character encoding. The cd argument is a...
iconv_close
The iconv_close() function deallocates a conversion descriptor cd previously allocated using iconv_open(3).
iconv_open
The iconv_open() function allocates a conversion descriptor suitable for converting byte sequences from character encoding fromcode to character encoding...
if_nameindex
The if_nameindex() function returns an array of if_nameindex structures, each containing information about one of the network interfaces on the local system.
if_nametoindex
The if_nametoindex() function returns the index of the network interface corresponding to the name ifname. The if_indextoname() function returns the name of the...
ilogb
These functions return the exponent part of their argument as a signed integer. When no error occurs, these functions are equivalent to the corresponding...
index
The index() function returns a pointer to the first occurrence of the character c in the string s. The rindex() function returns a pointer to the last...
inet
inet_aton() converts the Internet host address cp from the IPv4 numbers-and-dots notation into binary form (in network byte order) and stores it in the...
inet_net_pton
These functions convert network numbers between presentation (i.e., printable) format and network (i.e., binary) format. For both functions, af specifies the...
inet_ntop
This function converts the network address structure src in the af address family into a character string. The resulting string is copied to the buffer pointed...
inet_pton
This function converts the character string src into a network address structure in the af address family, then copies the network address structure to dst. The...
INFINITY
The macro INFINITY expands to a float constant representing positive infinity. The macro NAN expands to a float constant representing a quiet NaN (when...
infnan
The infnan() function returns a suitable value for infinity and "not-a-number" (NaN) results. The value of error can be ERANGE to represent infinity or anything...
initgroups
The initgroups() function initializes the group access list by reading the group database /etc/group and using all groups of which user is a member. The...
insque
The insque() and remque() functions manipulate doubly-linked lists. Each element in the list is a structure of which the first two elements are a forward and a...
intro
Section 3 of the manual describes all library functions excluding the library functions (system call wrappers) described in Section 2, which implement system...
isalpha
These functions check whether c, which must have the value of an unsigned char or EOF, falls into a certain character class according to the specified locale...
isatty
The isatty() function tests whether fd is an open file descriptor referring to a terminal.
isfdtype
The isfdtype() function tests whether the file descriptor fd refers to a file of type fdtype. The fdtype argument specifies one of the S_IF* constants defined...
isgreater
The normal relational operations (like <, "less than") will fail if one of the operands is NaN. This will cause an exception. To avoid this, C99 defines the...
iswalnum
The iswalnum() function is the wide-character equivalent of the isalnum(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswalpha
The iswalpha() function is the wide-character equivalent of the isalpha(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswblank
The iswblank() function is the wide-character equivalent of the isblank(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswcntrl
The iswcntrl() function is the wide-character equivalent of the iscntrl(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswctype
If wc is a wide character having the character property designated by desc (or in other words: belongs to the character class designated by desc), the...
iswdigit
The iswdigit() function is the wide-character equivalent of the isdigit(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswgraph
The iswgraph() function is the wide-character equivalent of the isgraph(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswlower
The iswlower() function is the wide-character equivalent of the islower(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswprint
The iswprint() function is the wide-character equivalent of the isprint(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswpunct
The iswpunct() function is the wide-character equivalent of the ispunct(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswspace
The iswspace() function is the wide-character equivalent of the isspace(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswupper
The iswupper() function is the wide-character equivalent of the isupper(3) function. It tests whether wc is a wide character belonging to the wide-character...
iswxdigit
The iswxdigit() function is the wide-character equivalent of the isxdigit(3) function. It tests whether wc is a wide character belonging to the wide-character...
j0
The j0() and j1() functions return Bessel functions of x of the first kind of orders 0 and 1, respectively. The jn() function returns the Bessel function of x...
key_setsecret
The functions here are used within the RPC's secure authentication mechanism (AUTH_DES). There should be no need for user programs to use this functions. The...
ldexp
These functions return the result of multiplying the floating-point number x by 2 raised to the power exp.
lgamma
For the definition of the Gamma function, see tgamma(3). The lgamma(), lgammaf(), and lgammal() functions return the natural logarithm of the absolute value of...
lio_listio
The lio_listio() function initiates the list of I/O operations described by the array aiocb_list.
localeconv
The localeconv() function returns a pointer to a struct lconv for the current locale. This structure is shown in locale(7), and contains all values associated...
lockf
Apply, test or remove a POSIX lock on a section of an open file. The file is specified by fd, a file descriptor open for writing, the action by cmd, and the...
log
These functions return the natural logarithm of x.
log10
These functions return the base 10 logarithm of x.
log1p
These functions return a value equivalent to
log2
These functions return the base 2 logarithm of x.
logb
These functions extract the exponent from the internal floating-point representation of x and return it as a floating-point value. The integer constant...
login
The utmp file records who is currently using the system. The wtmp file records all logins and logouts. See utmp(5). The function login() takes the supplied...
lrint
These functions round their argument to the nearest integer value, using the current rounding direction (see fesetround(3)). Note that unlike the rint(3) family...
lround
These functions round their argument to the nearest integer value, rounding away from zero, regardless of the current rounding direction (see fenv(3)). Note...
lsearch
lfind() and lsearch() perform a linear search for key in the array base which has *nmemb elements of size bytes each. The comparison function referenced by...
lseek64
The lseek(2) family of functions reposition the offset of the open file associated with the file descriptor fd to offset bytes relative to the start, current...
makecontext
In a System V-like environment, one has the type ucontext_t defined in <ucontext.h> and the four functions getcontext(3), setcontext(3), makecontext() and...
makedev
A device ID consists of two parts: a major ID, identifying the class of the device, and a minor ID, identifying a specific instance of a device in that class. A...
mallinfo
The mallinfo() function returns a copy of a structure containing information about memory allocations performed by malloc(3) and related functions.
malloc
The malloc() function allocates size bytes and returns a pointer to the allocated memory. The memory is not initialized. If size is 0, then malloc() returns...
malloc_get_state
The malloc_get_state() function records the current state of all malloc(3) internal bookkeeping variables (but not the actual contents of the heap or the state...
malloc_hook
The GNU C library lets you modify the behavior of malloc(3), realloc(3), and free(3) by specifying appropriate hook functions. You can use these hooks to help...
malloc_info
The malloc_info() function exports an XML string that describes the current state of the memory-allocation implementation in the caller. The string is printed...
malloc_stats
The malloc_stats() function prints (on standard error) statistics about memory allocated by malloc(3) and related functions. For each arena (allocation area)...
malloc_trim
The malloc_trim() function attempts to release free memory at the top of the heap (by calling sbrk(2) with a suitable argument). The pad argument specifies the...
malloc_usable_size
The malloc_usable_size() function returns the number of usable bytes in the block pointed to by ptr, a pointer to a block of memory allocated by malloc(3) or a...
mallopt
The mallopt() function adjusts parameters that control the behavior of the memory-allocation functions (see malloc(3)). The param argument specifies the...
matherr
The System V Interface Definition (SVID) specifies that various math functions should invoke a function called matherr() if a math exception is detected. This...
MB_CUR_MAX
The MB_CUR_MAX macro defines an integer expression giving the maximum number of bytes needed to represent a single wide character in the current locale. It is...
mblen
If s is not NULL, the mblen() function inspects at most n bytes of the multibyte string starting at s and extracts the next complete multibyte character. It...
MB_LEN_MAX
The MB_LEN_MAX macro is the upper bound for the number of bytes needed to represent a single wide character, in any of the supported locales.
mbrlen
The mbrlen() function inspects at most n bytes of the multibyte string starting at s and extracts the next complete multibyte character. It updates the shift...
mbrtowc
The main case for this function is when s is not NULL and pwc is not NULL. In this case, the mbrtowc() function inspects at most n bytes of the multibyte string...
mbsinit
Character conversion between the multibyte representation and the wide character representation uses conversion state, of type mbstate_t. Conversion of a string...
mbsnrtowcs
The mbsnrtowcs() function is like the mbsrtowcs(3) function, except that the number of bytes to be converted, starting at *src, is limited to nms. If dest is...
mbsrtowcs
If dest is not NULL, the mbsrtowcs() function converts the multibyte string *src to a wide-character string starting at dest. At most len wide characters are...
mbstowcs
If dest is not NULL, the mbstowcs() function converts the multibyte string src to a wide-character string starting at dest. At most n wide characters are...
mbtowc
The main case for this function is when s is not NULL and pwc is not NULL. In this case, the mbtowc() function inspects at most n bytes of the multibyte string...
mcheck
The mcheck() function installs a set of debugging hooks for the malloc(3) family of memory-allocation functions. These hooks cause certain consistency checks to...
memccpy
The memccpy() function copies no more than n bytes from memory area src to memory area dest, stopping when the character c is found. If the memory areas...
memchr
The memchr() function scans the initial n bytes of the memory area pointed to by s for the first instance of c. Both c and the bytes of the memory area pointed...
memcmp
The memcmp() function compares the first n bytes (each interpreted as unsigned char) of the memory areas s1 and s2.
memcpy
The memcpy() function copies n bytes from memory area src to memory area dest. The memory areas must not overlap. Use memmove(3) if the memory areas do overlap.
memfrob
The memfrob() function encrypts the first n bytes of the memory area s by exclusive-ORing each character with the number 42. The effect can be reversed by using...
memmem
The memmem() function finds the start of the first occurrence of the substring needle of length needlelen in the memory area haystack of length haystacklen.
memmove
The memmove() function copies n bytes from memory area src to memory area dest. The memory areas may overlap: copying takes place as though the bytes in src are...
mempcpy
The mempcpy() function is nearly identical to the memcpy(3) function. It copies n bytes from the object beginning at src into the object pointed to by dest. But...
memset
The memset() function fills the first n bytes of the memory area pointed to by s with the constant byte c.
mkdtemp
The mkdtemp() function generates a uniquely named temporary directory from template. The last six characters of template must be XXXXXX and these are replaced...
mkfifo
mkfifo() makes a FIFO special file with name pathname. mode specifies the FIFO's permissions. It is modified by the process's umask in the usual way: the...
mkstemp
The mkstemp() function generates a unique temporary filename from template, creates and opens the file, and returns an open file descriptor for the file. The...
mktemp
Never use this function; see Bugs. The mktemp() function generates a unique temporary filename from template. The last six characters of template must be XXXXXX...
modf
These functions break the argument x into an integral part and a fractional part, each of which has the same sign as x. The integral part is stored in the...
mq_close
mq_close() closes the message queue descriptor mqdes. If the calling process has attached a notification request to this message queue via mqdes, then this...
mq_getattr
mq_getattr() and mq_setattr() respectively retrieve and modify attributes of the message queue referred to by the message queue descriptor mqdes. mq_getattr()...
mq_notify
mq_notify() allows the calling process to register or unregister for delivery of an asynchronous notification when a new message arrives on the empty message...
mq_open
mq_open() creates a new POSIX message queue or opens an existing queue. The queue is identified by name. For details of the construction of name, see...
mq_receive
mq_receive() removes the oldest message with the highest priority from the message queue referred to by the message queue descriptor mqdes, and places it in the...
mq_send
mq_send() adds the message pointed to by msg_ptr to the message queue referred to by the message queue descriptor mqdes. The msg_len argument specifies the...
mq_unlink
mq_unlink() removes the specified message queue name. The message queue name is removed immediately. The queue itself is destroyed once any other processes that...
mtrace
The mtrace() function installs hook functions for the memory-allocation functions (malloc(3), realloc(3) memalign(3), free(3)). These hook functions record...
nan
These functions return a representation (determined by tagp) of a quiet NaN. If the implementation does not support quiet NaNs, these functions return zero.
netlink
<linux/netlink.h> defines several standard macros to access or create a netlink datagram. They are similar in spirit to the macros defined in cmsg(3) for...
newlocale
The newlocale() function creates a new locale object, or modifies an existing object, returning a reference to the new or modified object as the function...
nextafter
The nextafter(), nextafterf(), and nextafterl() functions return the next representable floating-point value following x in the direction of y. If y is less...
nextup
The nextup(), nextupf(), and nextupl() functions return the next representable floating-point number greater than x. If x is the smallest representable negative...
nl_langinfo
The nl_langinfo() and nl_langinfo_l() functions provide access to locale information in a more flexible way than localeconv(3). nl_langinfo() returns a string...
ntp_gettime
get time parameters (NTP daemon interface)
offsetof
The macro offsetof() returns the offset of the field member from the start of the structure type. This macro is useful because the sizes of the fields that...
on_exit
The on_exit() function registers the given function to be called at normal process termination, whether via exit(3) or via return from the program's main(). The...
opendir
The opendir() function opens a directory stream corresponding to the directory name, and returns a pointer to the directory stream. The stream is positioned at...
open_memstream
The open_memstream() function opens a stream for writing to a memory buffer. The function dynamically allocates the buffer, and the buffer automatically grows...
openpty
The openpty() function finds an available pseudoterminal and returns file descriptors for the master and slave in amaster and aslave. If name is not NULL, the...
perror
The perror() function produces a message on standard error describing the last error encountered during a call to a system or library function. First (if s is...
popen
The popen() function opens a process by creating a pipe, forking, and invoking the shell. Since a pipe is by definition unidirectional, the type argument may...
posix_fallocate
The function posix_fallocate() ensures that disk space is allocated for the file referred to by the file descriptor fd for the bytes in the range starting at...
posix_madvise
The posix_madvise() function allows an application to advise the system about its expected patterns of usage of memory in the address range starting at addr and...
posix_memalign
The function posix_memalign() allocates size bytes and places the address of the allocated memory in *memptr. The address of the allocated memory will be a...
posix_openpt
The posix_openpt() function opens an unused pseudoterminal master device, returning a file descriptor that can be used to refer to that device.
posix_spawn
The posix_spawn() and posix_spawnp() functions are used to create a new child process that executes a specified file. These functions were specified by POSIX to...
pow
These functions return the value of x raised to the power of y.
pow10
These functions return the value of 10 raised to the power x.
__ppc_get_timebase
__ppc_get_timebase() reads the current value of the Time Base Register and returns its value, while __ppc_get_timebase_freq() returns the frequency in which the...
__ppc_set_ppr_med
These functions provide access to the Program Priority Register (PPR) on the Power architecture. The PPR is a 64-bit register that controls the program's...
__ppc_yield
These functions provide hints about the usage of resources that are shared with other processors on the Power architecture. They can be used, for example, if a...
printf
The functions in the printf() family produce output according to a format as described below. The functions printf() and vprintf() write output to stdout, the...
profil
This routine provides a means to find out in what areas your program spends most of its time. The argument buf points to bufsiz bytes of core. Every virtual 10...
program_invocation_name
program_invocation_name contains the name that was used to invoke the calling program. This is the same as the value of argv[0] in main(), with the difference...
psignal
The psignal() function displays a message on stderr consisting of the string s, a colon, a space, a string describing the signal number sig, and a trailing...
pthread_attr_init
The pthread_attr_init() function initializes the thread attributes object pointed to by attr with default attribute values. After this call, individual...
pthread_attr_setaffinity_np
The pthread_attr_setaffinity_np() function sets the CPU affinity mask attribute of the thread attributes object referred to by attr to the value specified in...
pthread_attr_setdetachstate
The pthread_attr_setdetachstate() function sets the detach state attribute of the thread attributes object referred to by attr to the value specified in...
pthread_attr_setguardsize
The pthread_attr_setguardsize() function sets the guard size attribute of the thread attributes object referred to by attr to the value specified in guardsize...
pthread_attr_setinheritsched
The pthread_attr_setinheritsched() function sets the inherit-scheduler attribute of the thread attributes object referred to by attr to the value specified in...
pthread_attr_setschedparam
The pthread_attr_setschedparam() function sets the scheduling parameter attributes of the thread attributes object referred to by attr to the values specified...
pthread_attr_setschedpolicy
The pthread_attr_setschedpolicy() function sets the scheduling policy attribute of the thread attributes object referred to by attr to the value specified in...
pthread_attr_setscope
The pthread_attr_setscope() function sets the contention scope attribute of the thread attributes object referred to by attr to the value specified in scope...
pthread_attr_setstack
The pthread_attr_setstack() function sets the stack address and stack size attributes of the thread attributes object referred to by attr to the values...
pthread_attr_setstackaddr
These functions are obsolete: do not use them. Use pthread_attr_setstack(3) and pthread_attr_getstack(3) instead. The pthread_attr_setstackaddr() function sets...
pthread_attr_setstacksize
The pthread_attr_setstacksize() function sets the stack size attribute of the thread attributes object referred to by attr to the value specified in stacksize...
pthread_cancel
The pthread_cancel() function sends a cancellation request to the thread thread. Whether and when the target thread reacts to the cancellation request depends...
pthread_cleanup_push
These functions manipulate the calling thread's stack of thread-cancellation clean-up handlers. A clean-up handler is a function that is automatically executed...
pthread_cleanup_push_defer_np
These functions are the same as pthread_cleanup_push(3) and pthread_cleanup_pop(3), except for the differences noted on this page. Like pthread_cleanup_push(3)...
pthread_create
The pthread_create() function starts a new thread in the calling process. The new thread starts execution by invoking start_routine(); arg is passed as the sole...
pthread_detach
The pthread_detach() function marks the thread identified by thread as detached. When a detached thread terminates, its resources are automatically released...
pthread_equal
The pthread_equal() function compares two thread identifiers.
pthread_exit
The pthread_exit() function terminates the calling thread and returns a value via retval that (if the thread is joinable) is available to another thread in the...
pthread_getattr_np
The pthread_getattr_np() function initializes the thread attributes object referred to by attr so that it contains actual attribute values describing the...
pthread_getcpuclockid
The pthread_getcpuclockid() function returns the clock ID for the CPU time clock of the thread thread.
pthread_join
The pthread_join() function waits for the thread specified by thread to terminate. If that thread has already terminated, then pthread_join() returns...
pthread_kill
The pthread_kill() function sends the signal sig to thread, a thread in the same process as the caller. The signal is asynchronously directed to thread. If sig...
pthread_kill_other_threads_np
pthread_kill_other_threads_np() has an effect only in the LinuxThreads threading implementation. On that implementation, calling this function causes the...
pthread_rwlockattr_setkind_np
The pthread_rwlockattr_setkind_np() function sets the "lock kind" attribute of the read-write lock attribute object referred to by attr to the value specified...
pthread_self
The pthread_self() function returns the ID of the calling thread. This is the same value that is returned in *thread in the pthread_create(3) call that created...
pthread_setaffinity_np
The pthread_setaffinity_np() function sets the CPU affinity mask of the thread thread to the CPU set pointed to by cpuset. If the call is successful, and the...
pthread_setcancelstate
The pthread_setcancelstate() sets the cancelability state of the calling thread to the value given in state. The previous cancelability state of the thread is...
pthread_setconcurrency
The pthread_setconcurrency() function informs the implementation of the application's desired concurrency level, specified in new_level. The implementation...
pthread_setname_np
By default, all the threads created using pthread_create() inherit the program name. The pthread_setname_np() function can be used to set a unique name for a...
pthread_setschedparam
The pthread_setschedparam() function sets the scheduling policy and parameters of the thread thread. policy specifies the new scheduling policy for thread. The...
pthread_setschedprio
The pthread_setschedprio() function sets the scheduling priority of the thread thread to the value specified in prio. (By contrast pthread_setschedparam(3)...
pthread_sigmask
The pthread_sigmask() function is just like sigprocmask(2), with the difference that its use in multithreaded programs is explicitly specified by POSIX.1. Other...
pthread_sigqueue
The pthread_sigqueue() function performs a similar task to sigqueue(3), but, rather than sending a signal to a process, it sends a signal to a thread in the...
pthread_testcancel
Calling pthread_testcancel() creates a cancellation point within the calling thread, so that a thread that is otherwise executing code that contains no...
pthread_tryjoin_np
These functions operate in the same way as pthread_join(3), except for the differences described on this page. The pthread_tryjoin_np() function performs a...
pthread_yield
pthread_yield() causes the calling thread to relinquish the CPU. The thread is placed at the end of the run queue for its static priority and another thread is...
ptsname
The ptsname() function returns the name of the slave pseudoterminal device corresponding to the master referred to by fd. The ptsname_r() function is the...
putenv
The putenv() function adds or changes the value of environment variables. The argument string is of the form name=value. If name does not already exist in the...
putgrent
The putgrent() function is the counterpart for fgetgrent(3). The function writes the content of the provided struct group into the stream. The list of group...
putpwent
The putpwent() function writes a password entry from the structure p in the file associated with stream.
puts
fputc() writes the character c, cast to an unsigned char, to stream. fputs() writes the string s to stream, without its terminating null byte ('\0'). putc() is...
putwchar
The putwchar() function is the wide-character equivalent of the putchar(3) function. It writes the wide character wc to stdout. If ferror(stdout) becomes true...
qecvt
The functions qecvt(), qfcvt(), and qgcvt() are identical to ecvt(3), fcvt(3), and gcvt(3) respectively, except that they use a long double argument number. See...
qsort
The qsort() function sorts an array with nmemb elements of size size. The base argument points to the start of the array. The contents of the array are sorted...
queue
These macros define and operate on four types of data structures: singly-linked lists, singly-linked tail queues, lists, and tail queues. All four structures...
raise
The raise() function sends a signal to the calling process or thread. In a single-threaded program it is equivalent to
rand
The rand() function returns a pseudo-random integer in the range 0 to RAND_MAX inclusive (i.e., the mathematical range [0, RAND_MAX]). The srand() function sets...
random
The random() function uses a nonlinear additive feedback random number generator employing a default table of size 31 long integers to return successive...
random_r
These functions are the reentrant equivalents of the functions described in random(3). They are suitable for use in multithreaded programs where each thread...
rcmd
The rcmd() function is used by the superuser to execute a command on a remote machine using an authentication scheme based on privileged port numbers. The...
readdir
The readdir() function returns a pointer to a dirent structure representing the next directory entry in the directory stream pointed to by dirp. It returns NULL...
readdir_r
This function is deprecated; use readdir(3) instead. The readdir_r() function was invented as a reentrant version of readdir(3). It reads the next directory...
realpath
realpath() expands all symbolic links and resolves references to /./, /../ and extra '/' characters in the null-terminated string named by path to produce a...
re_comp
re_comp() is used to compile the null-terminated regular expression pointed to by regex. The compiled pattern occupies a static area, the pattern buffer, which...
regex
POSIX regex compiling regcomp() is used to compile a regular expression into a form that is suitable for subsequent regexec() searches. regcomp() is supplied...
remainder
These functions compute the remainder of dividing x by y. The return value is x-n*y, where n is the value x / y, rounded to the nearest integer. If the absolute...
remove
remove() deletes a name from the filesystem. It calls unlink(2) for files, and rmdir(2) for directories. If the removed name was the last link to a file and no...
remquo
These functions compute the remainder and part of the quotient upon division of x by y. A few bits of the quotient are stored via the quo pointer. The remainder...
resolver
Note: This page is incomplete (various resolver functions provided by glibc are not described) and likely out of date. The functions described below make...
rewinddir
The rewinddir() function resets the position of the directory stream dirp to the beginning of the directory.
rexec
This interface is obsoleted by rcmd(3). The rexec() function looks up the host *ahost using gethostbyname(3), returning -1 if the host does not exist...
rint
The nearbyint(), nearbyintf(), and nearbyintl() functions round their argument to an integer value in floating-point format, using the current rounding...
round
These functions round x to the nearest integer, but round halfway cases away from zero (regardless of the current rounding direction, see fenv(3)), instead of...
rpc
These routines allow C programs to make procedure calls on other machines across the network. First, the client calls a procedure to send a data packet to the...
rpmatch
rpmatch() handles a user response to yes or no questions, with support for internationalization. response should be a null-terminated string containing a...
rtime
This function uses the Time Server Protocol as described in RFC 868 to obtain the time from a remote machine. The Time Server Protocol gives the time in seconds...
rtnetlink
All rtnetlink(7) messages consist of a netlink(7) message header and appended attributes. The attributes should be manipulated only using the macros provided...
scalb
multiply floating-point number by integral power of radix (OBSOLETE)
scalbln
multiply floating-point number by integral power of radix
scandir
The scandir() function scans the directory dirp, calling filter() on each directory entry. Entries for which filter() returns nonzero are stored in strings...
scanf
The scanf() family of functions scans input according to format as described below. This format may contain conversion specifications; the results from such...
sched_getcpu
sched_getcpu() returns the number of the CPU on which the calling thread is currently executing.
seekdir
The seekdir() function sets the location in the directory stream from which the next readdir(2) call will start. The loc argument should be a value returned by...
sem_close
sem_close() closes the named semaphore referred to by sem, allowing any resources that the system has allocated to the calling process for this semaphore to be...
sem_destroy
sem_destroy() destroys the unnamed semaphore at the address pointed to by sem. Only a semaphore that has been initialized by sem_init(3) should be destroyed...
sem_getvalue
sem_getvalue() places the current value of the semaphore pointed to sem into the integer pointed to by sval. If one or more processes or threads are blocked...
sem_init
sem_init() initializes the unnamed semaphore at the address pointed to by sem. The value argument specifies the initial value for the semaphore. The pshared...
sem_open
sem_open() creates a new POSIX semaphore or opens an existing semaphore. The semaphore is identified by name. For details of the construction of name, see...
sem_post
sem_post() increments (unlocks) the semaphore pointed to by sem. If the semaphore's value consequently becomes greater than zero, then another process or thread...
sem_unlink
sem_unlink() removes the named semaphore referred to by name. The semaphore name is removed immediately. The semaphore is destroyed once all other processes...
sem_wait
sem_wait() decrements (locks) the semaphore pointed to by sem. If the semaphore's value is greater than zero, then the decrement proceeds, and the function...
setaliasent
One of the databases available with the Name Service Switch (NSS) is the aliases database, that contains mail aliases. (To find out which databases are...
setbuf
The three types of buffering available are unbuffered, block buffered, and line buffered. When an output stream is unbuffered, information appears on the...
setenv
The setenv() function adds the variable name to the environment with the value value, if name does not already exist. If name does exist in the environment...
__setfpucw
__setfpucw() transfers control_word to the registers of the FPU (floating-point unit) on the i386 architecture. This was used to control floating-point...
setjmp
The functions described on this page are used for performing "nonlocal gotos": transferring execution from one function to a predetermined location in another...
setlocale
The setlocale() function is used to set or query the program's current locale. If locale is not NULL, the program's current locale is modified according to the...
setlogmask
A process has a log priority mask that determines which calls to syslog(3) may be logged. All other calls will be ignored. Logging is enabled for the priorities...
setnetgrent
The netgroup is a SunOS invention. A netgroup database is a list of string triples (hostname, username, domainname) or other netgroup names. Any of the elements...
shm_open
shm_open() creates and opens a new, or opens an existing, POSIX shared memory object. A POSIX shared memory object is in effect a handle which can be used by...
siginterrupt
The siginterrupt() function changes the restart behavior when a system call is interrupted by the signal sig. If the flag argument is false (0), then system...
signbit
signbit() is a generic macro which can work on all real floating-point types. It returns a nonzero value if the value of x has its sign bit set. This is not the...
significand
These functions return the mantissa of x scaled to the range [1,2). They are equivalent to scalb(x, (double) -ilogb(x)) This function exists mainly for use in...
sigpause
Don't use this function. Use sigsuspend(2) instead. The function sigpause() is designed to wait for some signal. It changes the process's signal mask (set of...
sigqueue
sigqueue() sends the signal specified in sig to the process whose PID is given in pid. The permissions required to send a signal are the same as for kill(2). As...
sigset
These functions are provided in glibc as a compatibility interface for programs that make use of the historical System V signal API. This API is obsolete: new...
sigsetops
These functions allow the manipulation of POSIX signal sets. sigemptyset() initializes the signal set given by set to empty, with all signals excluded from the...
sigvec
These functions are provided in glibc as a compatibility interface for programs that make use of the historical BSD signal API. This API is obsolete: new...
sigwait
The sigwait() function suspends execution of the calling thread until one of the signals specified in the signal set set becomes pending. The function accepts...
sin
These functions return the sine of x, where x is given in radians.
sincos
Several applications need sine and cosine of the same angle x. These functions compute both at the same time, and store the results in *sin and *cos. If x is a...
sinh
hyperbolic sine function
sleep
sleep() makes the calling thread sleep until seconds seconds have elapsed or a signal arrives which is not ignored.
sockatmark
sockatmark() returns a value indicating whether or not the socket referred to by the file descriptor sockfd is at the out-of-band mark. If the socket is at the...
sqrt
These functions return the nonnegative square root of x.
statvfs
The function statvfs() returns information about a mounted filesystem. path is the pathname of any file within the mounted filesystem.
stdarg
A function may be called with a varying number of arguments of varying types. The include file <stdarg.h> declares a type va_list and defines three macros for...
stdin
Under normal circumstances every UNIX program has three streams opened for it when it starts up, one for input, one for output, and one for printing diagnostic...
stdio
The standard I/O library provides a simple and efficient buffered stream I/O interface. Input and output is mapped into logical data streams and the physical...
stdio_ext
Solaris introduced routines to allow portable access to the internals of the FILE structure, and glibc also implemented these. The __fbufsize() function returns...
stpcpy
The stpcpy() function copies the string pointed to by src (including the terminating null byte ('\0')) to the array pointed to by dest. The strings may not...
stpncpy
The stpncpy() function copies at most n characters from the string pointed to by src, including the terminating null byte ('\0'), to the array pointed to by...
strcasecmp
The strcasecmp() function performs a byte-by-byte comparison of the strings s1 and s2, ignoring the case of the characters. It returns an integer less than...
strcat
The strcat() function appends the src string to the dest string, overwriting the terminating null byte ('\0') at the end of dest, and then adds a terminating...
strchr
The strchr() function returns a pointer to the first occurrence of the character c in the string s. The strrchr() function returns a pointer to the last...
strcmp
The strcmp() function compares the two strings s1 and s2. It returns an integer less than, equal to, or greater than zero if s1 is found, respectively, to be...
strcoll
The strcoll() function compares the two strings s1 and s2. It returns an integer less than, equal to, or greater than zero if s1 is found, respectively, to be...
strcpy
The strcpy() function copies the string pointed to by src, including the terminating null byte ('\0'), to the buffer pointed to by dest. The strings may not...
strdup
The strdup() function returns a pointer to a new string which is a duplicate of the string s. Memory for the new string is obtained with malloc(3), and can be...
strerror
The strerror() function returns a pointer to a string that describes the error code passed in the argument errnum, possibly using the LC_MESSAGES part of the...
strfmon
The strfmon() function formats the specified monetary amount according to the current locale and format specification format and places the result in the...
strfry
The strfry() function randomizes the contents of string by using rand(3) to randomly swap characters in the string. The result is an anagram of string.
strftime
The strftime() function formats the broken-down time tm according to the format specification format and places the result in the character array s of size max...
string
The string functions perform string operations on null-terminated strings. See the individual man pages for descriptions of each function.
strlen
The strlen() function calculates the length of the string pointed to by s, excluding the terminating null byte ('\0').
strnlen
The strnlen() function returns the number of characters in the string pointed to by s, excluding the terminating null byte ('\0'), but at most maxlen. In doing...
strpbrk
The strpbrk() function locates the first occurrence in the string s of any of the bytes in the string accept.
strptime
The strptime() function is the converse of strftime(3); it converts the character string pointed to by s to values which are stored in the "broken-down time"...
strsep
If *stringp is NULL, the strsep() function returns NULL and does nothing else. Otherwise, this function finds the first token in the string *stringp, that is...
strsignal
The strsignal() function returns a string describing the signal number passed in the argument sig. The string can be used only until the next call to...
strspn
The strspn() function calculates the length (in bytes) of the initial segment of s which consists entirely of bytes in accept. The strcspn() function calculates...
strstr
The strstr() function finds the first occurrence of the substring needle in the string haystack. The terminating null bytes ('\0') are not compared. The...
strtod
The strtod(), strtof(), and strtold() functions convert the initial portion of the string pointed to by nptr to double, float, and long double representation...
strtoimax
These functions are just like strtol(3) and strtoul(3), except that they return a value of type intmax_t and uintmax_t, respectively.
strtok
The strtok() function breaks a string into a sequence of zero or more nonempty tokens. On the first call to strtok(), the string to be parsed should be...
strtol
The strtol() function converts the initial part of the string in nptr to a long integer value according to the given base, which must be between 2 and 36...
strtoul
The strtoul() function converts the initial part of the string in nptr to an unsigned long int value according to the given base, which must be between 2 and 36...
strverscmp
Often one has files jan1, jan2, ..., jan9, jan10, ... and it feels wrong when ls(1) orders them jan1, jan10, ..., jan2, ..., jan9. In order to rectify this, GNU...
strxfrm
The strxfrm() function transforms the src string into a form such that the result of strcmp(3) on two strings that have been transformed with strxfrm() is the...
swab
The swab() function copies n bytes from the array pointed to by from to the array pointed to by to, exchanging adjacent even and odd bytes. This function is...
sysconf
POSIX allows an application to test at compile or run time whether certain options are supported, or what the value is of certain configurable constants or...
syslog
closelog() closes the file descriptor being used to write to the system logger. The use of closelog() is optional. openlog() opens a connection to the system...
system
The system() library function uses fork(2) to create a child process that executes the shell command specified in command using execl(3) as follows...
sysv_signal
The sysv_signal() function takes the same arguments, and performs the same task, as signal(2). However sysv_signal() provides the System V unreliable signal...
tan
These functions return the tangent of x, where x is given in radians.
tanh
hyperbolic tangent function
tcgetpgrp
The function tcgetpgrp() returns the process group ID of the foreground process group on the terminal associated to fd, which must be the controlling terminal...
tcgetsid
The function tcgetsid() returns the session ID of the current session that has the terminal associated to fd as controlling terminal. This terminal must be the...
telldir
The telldir() function returns the current location associated with the directory stream dirp.
tempnam
Never use this function. Use mkstemp(3) or tmpfile(3) instead. The tempnam() function returns a pointer to a string that is a valid filename, and such that a...
termios
The termios functions describe a general terminal interface that is provided to control asynchronous communications ports.The termios structure Many of the...
tgamma
These functions calculate the Gamma function of x. The Gamma function is defined by Gamma(x) = integral from 0 to infinity of t^(x-1) e^-t dt It is defined for...
timegm
The functions timelocal() and timegm() are the inverses of localtime(3) and gmtime(3). Both functions take a broken-down time and convert it to calendar time...
timeradd
timeval operations
tmpfile
The tmpfile() function opens a unique temporary file in binary read/write (w+b) mode. The file will be automatically deleted when it is closed or the program...
tmpnam
Note: Avoid use of tmpnam(); use mkstemp(3) or tmpfile(3) instead. The tmpnam() function returns a pointer to a string that is a valid filename, and such that a...
toascii
toascii() converts c to a 7-bit unsigned char value that fits into the ASCII character set, by clearing the high-order bits.
toupper
These functions convert lowercase letters to uppercase, and vice versa. If c is a lowercase letter, toupper() returns its uppercase equivalent, if an uppercase...
towctrans
If wc is a wide character, the towctrans() function translates it according to the transliteration descriptor desc. If wc is WEOF, WEOF is returned. desc must...
towlower
The towlower() function is the wide-character equivalent of the tolower(3) function. If wc is an uppercase wide character, and there exists a lowercase...
towupper
The towupper() function is the wide-character equivalent of the toupper(3) function. If wc is a lowercase wide character, and there exists an uppercase...
trunc
These functions round x to the nearest integer not larger in absolute value.
tsearch
tsearch(), tfind(), twalk(), and tdelete() manage a binary tree. They are generalized from Knuth (6.2.2) Algorithm T. The first field in each node of the tree...
ttyname
The function ttyname() returns a pointer to the null-terminated pathname of the terminal device that is open on the file descriptor fd, or NULL on error (for...
ttyslot
The legacy function ttyslot() returns the index of the current user's entry in some file. Now "What file?" you ask. Well, let's first look at some...
tzset
The tzset() function initializes the tzname variable from the TZ environment variable. This function is automatically called by the other time conversion...
ualarm
The ualarm() function causes the signal SIGALRM to be sent to the invoking process after (not less than) usecs microseconds. The delay may be lengthened...
ulimit
Warning: This routine is obsolete. Use getrlimit(2), setrlimit(2), and sysconf(3) instead. For the shell command ulimit(), see bash(1). The ulimit() call will...
undocumented
This man page mentions those library functions which are implemented in the standard libraries but not yet documented in man pages.Solicitation If you have...
ungetwc
The ungetwc() function is the wide-character equivalent of the ungetc(3) function. It pushes back a wide character onto stream and returns it. If wc is WEOF, it...
unlocked_stdio
Each of these functions has the same behavior as its counterpart without the "_unlocked" suffix, except that they do not use locking (they do not set locks...
unlockpt
The unlockpt() function unlocks the slave pseudoterminal device corresponding to the master pseudoterminal referred to by fd. unlockpt() should be called before...
updwtmp
updwtmp() appends the utmp structure ut to the wtmp file. logwtmp() constructs a utmp structure using line, name, host, current time and current process ID...
uselocale
The uselocale() function sets the current locale for the calling thread, and returns the thread's previously current locale. After a successful call to...
usleep
The usleep() function suspends execution of the calling thread for (at least) usec microseconds. The sleep may be lengthened slightly by any system activity or...
wcpcpy
The wcpcpy() function is the wide-character equivalent of the stpcpy(3) function. It copies the wide-character string pointed to by src, including the...
wcpncpy
The wcpncpy() function is the wide-character equivalent of the stpncpy(3) function. It copies at most n wide characters from the wide-character string pointed...
wcrtomb
The main case for this function is when s is not NULL and wc is not a null wide character (L'\0'). In this case, the wcrtomb() function converts the wide...
wcscasecmp
The wcscasecmp() function is the wide-character equivalent of the strcasecmp(3) function. It compares the wide-character string pointed to by s1 and the...
wcscat
The wcscat() function is the wide-character equivalent of the strcat(3) function. It copies the wide-character string pointed to by src, including the...
wcschr
The wcschr() function is the wide-character equivalent of the strchr(3) function. It searches the first occurrence of wc in the wide-character string pointed to...
wcscmp
The wcscmp() function is the wide-character equivalent of the strcmp(3) function. It compares the wide-character string pointed to by s1 and the wide-character...
wcscpy
The wcscpy() function is the wide-character equivalent of the strcpy(3) function. It copies the wide-character string pointed to by src, including the...
wcscspn
The wcscspn() function is the wide-character equivalent of the strcspn(3) function. It determines the length of the longest initial segment of wcs which...
wcsdup
The wcsdup() function is the wide-character equivalent of the strdup(3) function. It allocates and returns a new wide-character string whose initial contents is...
wcslen
The wcslen() function is the wide-character equivalent of the strlen(3) function. It determines the length of the wide-character string pointed to by s...
wcsncasecmp
The wcsncasecmp() function is the wide-character equivalent of the strncasecmp(3) function. It compares the wide-character string pointed to by s1 and the...
wcsncat
The wcsncat() function is the wide-character equivalent of the strncat(3) function. It copies at most n wide characters from the wide-character string pointed...
wcsncmp
The wcsncmp() function is the wide-character equivalent of the strncmp(3) function. It compares the wide-character string pointed to by s1 and the...
wcsncpy
The wcsncpy() function is the wide-character equivalent of the strncpy(3) function. It copies at most n wide characters from the wide-character string pointed...
wcsnlen
The wcsnlen() function is the wide-character equivalent of the strnlen(3) function. It returns the number of wide-characters in the string pointed to by s, not...
wcsnrtombs
The wcsnrtombs() function is like the wcsrtombs(3) function, except that the number of wide characters to be converted, starting at *src, is limited to nwc. If...
wcspbrk
The wcspbrk() function is the wide-character equivalent of the strpbrk(3) function. It searches for the first occurrence in the wide-character string pointed to...
wcsrchr
The wcsrchr() function is the wide-character equivalent of the strrchr(3) function. It searches the last occurrence of wc in the wide-character string pointed...
wcsrtombs
If dest is not NULL, the wcsrtombs() function converts the wide-character string *src to a multibyte string starting at dest. At most len bytes are written to...
wcsspn
The wcsspn() function is the wide-character equivalent of the strspn(3) function. It determines the length of the longest initial segment of wcs which consists...
wcsstr
The wcsstr() function is the wide-character equivalent of the strstr(3) function. It searches for the first occurrence of the wide-character string needle...
wcstoimax
These functions are just like wcstol(3) and wcstoul(3), except that they return a value of type intmax_t and uintmax_t, respectively.
wcstok
The wcstok() function is the wide-character equivalent of the strtok(3) function, with an added argument to make it multithread-safe. It can be used to split a...
wcstombs
If dest is not NULL, the wcstombs() function converts the wide-character string src to a multibyte string starting at dest. At most n bytes are written to dest...
wcswidth
The wcswidth() function returns the number of columns needed to represent the wide-character string pointed to by s, but at most n wide characters. If a...
wctob
The wctob() function tests whether the multibyte representation of the wide character c, starting in the initial state, consists of a single byte. If so, it is...
wctomb
If s is not NULL, the wctomb() function converts the wide character wc to its multibyte representation and stores it at the beginning of the character array...
wctrans
The wctrans_t type represents a mapping which can map a wide character to another wide character. Its nature is implementation-dependent, but the special value...
wctype
The wctype_t type represents a property which a wide character may or may not have. In other words, it represents a class of wide characters. This type's nature...
wcwidth
The wcwidth() function returns the number of columns needed to represent the wide character c. If c is a printable wide character, the value is at least 0. If c...
wmemchr
The wmemchr() function is the wide-character equivalent of the memchr(3) function. It searches the n wide characters starting at s for the first occurrence of...
wmemcmp
The wmemcmp() function is the wide-character equivalent of the memcmp(3) function. It compares the n wide-characters starting at s1 and the n wide-characters...
wmemcpy
The wmemcpy() function is the wide-character equivalent of the memcpy(3) function. It copies n wide characters from the array starting at src to the array...
wmemmove
The wmemmove() function is the wide-character equivalent of the memmove(3) function. It copies n wide characters from the array starting at src to the array...
wmemset
The wmemset() function is the wide-character equivalent of the memset(3) function. It fills the array of n wide-characters starting at wcs with n copies of the...
wordexp
The function wordexp() performs a shell-like expansion of the string s and returns the result in the structure pointed to by p. The data type wordexp_t is a...
wprintf
The wprintf() family of functions is the wide-character equivalent of the printf(3) family of functions. It performs formatted output of wide characters. The...
xcrypt
The function passwd2des() takes a character string passwd of arbitrary length and fills a character array key of length 8. The array key is suitable for use as...
xdr
These routines allow C programmers to describe arbitrary data structures in a machine-independent fashion. Data for remote procedure calls are transmitted using...
y0
The y0() and y1() functions return Bessel functions of x of the second kind of orders 0 and 1, respectively. The yn() function returns the Bessel function of x...
POSIX Functions (Section 3p)
a64l
These functions maintain numbers stored in radix-64 ASCII characters. This is a notation by which 32-bit integers can be represented by up to six characters...
abort
The abort() function shall cause abnormal process termination to occur, unless the signal SIGABRT is being caught and the signal handler does not return. The...
abs
The abs() function shall compute the absolute value of its integer operand, i. If the result cannot be represented, the behavior is undefined.
accept
The accept() function shall extract the first connection on the queue of pending connections, create a new socket with the same socket type protocol and address...
access
The access() function shall check the file named by the pathname pointed to by the path argument for accessibility according to the bit pattern contained in...
acos
These functions shall compute the principal value of the arc cosine of their argument x. The value of x should be in the range [-1,1]. An application wishing to...
acosh
These functions shall compute the inverse hyperbolic cosine of their argument x. An application wishing to check for error situations should set errno to zero...
acosl
arc cosine functions
aio_cancel
The aio_cancel() function shall attempt to cancel one or more asynchronous I/O requests currently outstanding against file descriptor fildes. The aiocbp...
aio_error
The aio_error() function shall return the error status associated with the aiocb structure referenced by the aiocbp argument. The error status for an...
aio_fsync
The aio_fsync() function shall asynchronously perform a file synchronization operation, as specified by the op argument, for I/O operations associated with the...
aio_read
The aio_read() function shall read aiocbp->aio_nbytes from the file associated with aiocbp->aio_fildes into the buffer pointed to by aiocbp->aio_buf. The...
aio_return
The aio_return() function shall return the return status associated with the aiocb structure referenced by the aiocbp argument. The return status for an...
aio_suspend
The aio_suspend() function shall suspend the calling thread until at least one of the asynchronous I/O operations referenced by the list argument has completed...
aio_write
The aio_write() function shall write aiocbp->aio_nbytes to the file associated with aiocbp->aio_fildes from the buffer pointed to by aiocbp->aio_buf. The...
alarm
The alarm() function shall cause the system to generate a SIGALRM signal for the process after the number of realtime seconds specified by seconds have elapsed...
alphasort
The alphasort() function can be used as the comparison function for the scandir() function to sort the directory entries, d1 and d2, into alphabetical order...
asctime
convert date and time to a string
asin
These functions shall compute the principal value of the arc sine of their argument x. The value of x should be in the range [-1,1]. An application wishing to...
asinh
These functions shall compute the inverse hyperbolic sine of their argument x. An application wishing to check for error situations should set errno to zero and...
asinl
arc sine function
assert
The assert() macro shall insert diagnostics into programs; it shall expand to a void expression. When it is executed, if expression (which shall have a scalar...
atan
These functions shall compute the principal value of the arc tangent of their argument x. An application wishing to check for error situations should set errno...
atan2
These functions shall compute the principal value of the arc tangent of y/x, using the signs of both arguments to determine the quadrant of the return value. An...
atanf
arc tangent function
atanh
These functions shall compute the inverse hyperbolic tangent of their argument x. An application wishing to check for error situations should set errno to zero...
atanl
arc tangent function
atexit
The atexit() function shall register the function pointed to by func, to be called without arguments at normal program termination. At normal program...
atof
convert a string to a double-precision number
atoi
convert a string to an integer
atol
convert a string to a long integer
basename
The basename() function shall take the pathname pointed to by path and return a pointer to the final component of the pathname, deleting any trailing '/'...
bind
The bind() function shall assign a local socket address address to a socket identified by descriptor socket that has no local socket address assigned. Sockets...
bsearch
The bsearch() function shall search an array of nel objects, the initial element of which is pointed to by base, for an element that matches the object pointed...
btowc
The btowc() function shall determine whether c constitutes a valid (one-byte) character in the initial shift state. The behavior of this function shall be...
cabs
These functions shall compute the complex absolute value (also called norm, modulus, or magnitude) of z.
cacos
These functions shall compute the complex arc cosine of z, with branch cuts outside the interval [-1, +1] along the real axis.
cacosh
These functions shall compute the complex arc hyperbolic cosine of z, with a branch cut at values less than 1 along the real axis.
cacosl
complex arc cosine functions
calloc
The calloc() function shall allocate unused space for an array of nelem elements each of whose size in bytes is elsize. The space shall be initialized to all...
carg
These functions shall compute the argument (also called phase angle) of z, with a branch cut along the negative real axis.
casin
These functions shall compute the complex arc sine of z, with branch cuts outside the interval [-1, +1] along the real axis.
casinh
These functions shall compute the complex arc hyperbolic sine of z, with branch cuts outside the interval [-i, +i] along the imaginary axis.
casinl
complex arc sine functions
catan
These functions shall compute the complex arc tangent of z, with branch cuts outside the interval [-i, +i] along the imaginary axis.
catanh
These functions shall compute the complex arc hyperbolic tangent of z, with branch cuts outside the interval [-1, +1] along the real axis.
catanl
complex arc tangent functions
catclose
The catclose() function shall close the message catalog identified by catd. If a file descriptor is used to implement the type nl_catd, that file descriptor...
catgets
The catgets() function shall attempt to read message msg_id, in set set_id, from the message catalog identified by catd. The catd argument is a message catalog...
catopen
The catopen() function shall open a message catalog and return a message catalog descriptor. The name argument specifies the name of the message catalog to be...
cbrt
These functions shall compute the real cube root of their argument x.
ccos
These functions shall compute the complex cosine of z.
ccosh
These functions shall compute the complex hyperbolic cosine of z.
ccosl
complex cosine functions
ceil
These functions shall compute the smallest integral value not less than x.
cexp
These functions shall compute the complex exponent of z, defined as ez.
cfgetispeed
The cfgetispeed() function shall extract the input baud rate from the termios structure to which the termios_p argument points. This function shall return...
cfgetospeed
The cfgetospeed() function shall extract the output baud rate from the termios structure to which the termios_p argument points. This function shall return...
cfsetispeed
The cfsetispeed() function shall set the input baud rate stored in the structure pointed to by termios_p to speed. There shall be no effect on the baud rates...
cfsetospeed
The cfsetospeed() function shall set the output baud rate stored in the structure pointed to by termios_p to speed. There shall be no effect on the baud rates...
chdir
The chdir() function shall cause the directory named by the pathname pointed to by the path argument to become the current working directory; that is, the...
chmod
The chmod() function shall change S_ISUID, S_ISGID, S_ISVTX, and the file permission bits of the file named by the pathname pointed to by the path argument to...
chown
The chown() function shall change the user and group ownership of a file. The path argument points to a pathname naming a file. The user ID and group ID of the...
cimag
These functions shall compute the imaginary part of z.
clearerr
The clearerr() function shall clear the end-of-file and error indicators for the stream to which stream points. The clearerr() function shall not change the...
clock
The clock() function shall return the implementation's best approximation to the processor time used by the process since the beginning of an...
clock_getcpuclockid
The clock_getcpuclockid() function shall return the clock ID of the CPU-time clock of the process specified by pid. If the process described by pid exists and...
clock_getres
The clock_getres() function shall return the resolution of any clock. Clock resolutions are implementation-defined and cannot be set by a process. If the...
clock_nanosleep
If the flag TIMER_ABSTIME is not set in the flags argument, the clock_nanosleep() function shall cause the current thread to be suspended from execution until...
clock_settime
clock and timer functions
clog
These functions shall compute the complex natural (base e) logarithm of z, with a branch cut along the negative real axis.
close
The close() function shall deallocate the file descriptor indicated by fildes. To deallocate means to make the file descriptor available for return by...
closedir
The closedir() function shall close the directory stream referred to by the argument dirp. Upon return, the value of dirp may no longer point to an accessible...
closelog
The syslog() function shall send a message to an implementation-defined logging facility, which may log it in an implementation-defined system log, write it to...
confstr
The confstr() function shall return configuration-defined string values. Its use and purpose are similar to sysconf(), but it is used where string values rather...
conj
These functions shall compute the complex conjugate of z, by reversing the sign of its imaginary part.
connect
The connect() function shall attempt to make a connection on a connection-mode socket or to set or reset the peer address of a connectionless-mode socket.
copysign
These functions shall produce a value with the magnitude of x and the sign of y. On implementations that represent a signed zero but do not treat negative zero...
cos
These functions shall compute the cosine of their argument x, measured in radians. An application wishing to check for error situations should set errno to zero...
cosh
These functions shall compute the hyperbolic cosine of their argument x. An application wishing to check for error situations should set errno to zero and call...
cosl
cosine function
cpow
These functions shall compute the complex power function xy, with a branch cut for the first parameter along the negative real axis.
cproj
These functions shall compute a projection of z onto the Riemann sphere: z projects to z, except that all complex infinities (even those with one infinite part...
creal
These functions shall compute the real part of z.
creat
create a new file or rewrite an existing one
crypt
The crypt() function is a string encoding function. The algorithm is implementation-defined. The key argument points to a string to be encoded.
csin
These functions shall compute the complex sine of z.
csinh
These functions shall compute the complex hyperbolic sine of z.
csinl
complex sine functions
csqrt
These functions shall compute the complex square root of z, with a branch cut along the negative real axis.
ctan
These functions shall compute the complex tangent of z.
ctanh
These functions shall compute the complex hyperbolic tangent of z.
ctanl
complex tangent functions
ctermid
The ctermid() function shall generate a string that, when used as a pathname, refers to the current controlling terminal for the current process. If ctermid()...
ctime
For ctime(): The ctime() function shall convert the time pointed to by clock, representing time in seconds since the Epoch, to local time in the form of a...
daylight
daylight savings time flag
dbm_clearerr
These functions create, access, and modify a database. A datum consists of at least two members, dptr and dsize. The dptr member points to an object that is...
difftime
The difftime() function shall compute the difference between two calendar times (as returned by time()): time1- time0.
dirfd
The dirfd() function shall return a file descriptor referring to the same directory as the dirp argument. This file descriptor shall be closed by a call to...
dirname
The dirname() function shall take a pointer to a character string that contains a pathname, and return a pointer to a string that is a pathname of the parent...
div
The div() function shall compute the quotient and remainder of the division of the numerator numer by the denominator denom. If the division is inexact, the...
dlclose
The dlclose() function shall inform the system that the symbol table handle specified by handle is no longer needed by the application. An application writer...
dlerror
The dlerror() function shall return a null-terminated character string (with no trailing <newline>) that describes the last error that occurred during dynamic...
dlopen
The dlopen() function shall make the symbols (function identifiers and data object identifiers) in the executable object file specified by file available to the...
dlsym
The dlsym() function shall obtain the address of a symbol (a function identifier or a data object identifier) defined in the symbol table identified by the...
dprintf
print formatted output
drand48
This family of functions shall generate pseudo-random numbers using a linear congruential algorithm and 48-bit integer arithmetic. The drand48() and erand48()...
dup
The dup() function provides an alternative interface to the service provided by fcntl() using the F_DUPFD command.
duplocale
The duplocale() function shall create a duplicate copy of the locale object referenced by the locobj argument. If the locobj argument is LC_GLOBAL_LOCALE...
encrypt
The encrypt() function shall provide access to an implementation-defined encoding algorithm. The key generated by setkey() is used to encrypt the string block...
endgrent
The getgrent() function shall return a pointer to a structure containing the broken-out fields of an entry in the group database. When first called, getgrent()...
endhostent
These functions shall retrieve information about hosts. This information is considered to be stored in a database that can be accessed sequentially or randomly...
endnetent
These functions shall retrieve information about networks. This information is considered to be stored in a database that can be accessed sequentially or...
endprotoent
These functions shall retrieve information about protocols. This information is considered to be stored in a database that can be accessed sequentially or...
endpwent
These functions shall retrieve information about users. The getpwent() function shall return a pointer to a structure containing the broken-out fields of an...
endservent
These functions shall retrieve information about network services. This information is considered to be stored in a database that can be accessed sequentially...
endutxent
These functions shall provide access to the user accounting database. The getutxent() function shall read the next entry from the user accounting database. If...
environ
Refer to exec and the Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment Variables.
erand48
generate uniformly distributed pseudo-random numbers
erf
error functions
erfc
These functions shall compute the complementary error function 1.0 - erf(x). An application wishing to check for error situations should set errno to zero and...
erff
error functions
errno
The lvalue errno is used by many functions to return error values. Many functions provide an error number in errno, which has type int and is defined in...
exec
The exec family of functions shall replace the current process image with a new process image. The new image shall be constructed from a regular, executable...
exit
The value of status may be 0, EXIT_SUCCESS, EXIT_FAILURE, or any other value, though only the least significant 8 bits (that is, status & 0377) shall be...
_Exit
For _Exit(): The value of status may be 0, EXIT_SUCCESS, EXIT_FAILURE, or any other value, though only the least significant 8 bits (that is, status & 0377)...
exp
These functions shall compute the base-e exponential of x. An application wishing to check for error situations should set errno to zero and call...
exp2
These functions shall compute the base-2 exponential of x. An application wishing to check for error situations should set errno to zero and call...
expm1
These functions shall compute ex-1.0. An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before...
fabs
These functions shall compute the absolute value of their argument x,|x|.
faccessat
determine accessibility of a file relative to directory file descriptor
fattach
The fattach() function shall attach a STREAMS-based file descriptor to a file, effectively associating a pathname with fildes. The application shall ensure that...
fchdir
The fchdir() function shall be equivalent to chdir() except that the directory that is to be the new current working directory is specified by the file...
fchmod
The fchmod() function shall be equivalent to chmod() except that the file whose permissions are changed is specified by the file descriptor fildes. If fildes...
fchmodat
change mode of a file relative to directory file descriptor
fchown
The fchown() function shall be equivalent to chown() except that the file whose owner and group are changed is specified by the file descriptor fildes.
fchownat
change owner and group of a file relative to directory file descriptor
fclose
The fclose() function shall cause the stream pointed to by stream to be flushed and the associated file to be closed. Any unwritten buffered data for the stream...
fcntl
The fcntl() function shall perform the operations described below on open files. The fildes argument is a file descriptor.
fdatasync
The fdatasync() function shall force all currently queued I/O operations associated with the file indicated by file descriptor fildes to the synchronized I/O...
FD_CLR
macros for synchronous I/O multiplexing
fdetach
The fdetach() function shall detach a STREAMS-based file from the file to which it was attached by a previous call to fattach(). The path argument points to the...
fdim
These functions shall determine the positive difference between their arguments. If x is greater than y, x-y is returned. If x is less than or equal to y, +0 is...
fdopen
The fdopen() function shall associate a stream with a file descriptor.
fdopendir
The fdopendir() function shall be equivalent to the opendir() function except that the directory is specified by a file descriptor rather than by a name. The...
feclearexcept
The feclearexcept() function shall attempt to clear the supported floating-point exceptions represented by excepts.
fegetenv
The fegetenv() function shall attempt to store the current floating-point environment in the object pointed to by envp. The fesetenv() function shall attempt to...
fegetexceptflag
The fegetexceptflag() function shall attempt to store an implementation-defined representation of the states of the floating-point status flags indicated by the...
fegetround
The fegetround() function shall get the current rounding direction. The fesetround() function shall establish the rounding direction represented by its argument...
feholdexcept
The feholdexcept() function shall save the current floating-point environment in the object pointed to by envp, clear the floating-point status flags, and then...
feof
The feof() function shall test the end-of-file indicator for the stream pointed to by stream. The feof() function shall not change the setting of errno if...
feraiseexcept
The feraiseexcept() function shall attempt to raise the supported floating-point exceptions represented by the argument excepts. The order in which these...
ferror
The ferror() function shall test the error indicator for the stream pointed to by stream. The ferror() function shall not change the setting of errno if stream...
fesetenv
set current floating-point environment
fesetexceptflag
Refer to fegetexceptflag().
fesetround
set current rounding direction
fetestexcept
The fetestexcept() function shall determine which of a specified subset of the floating-point exception flags are currently set. The excepts argument specifies...
feupdateenv
The feupdateenv() function shall attempt to save the currently raised floating-point exceptions in its automatic storage, attempt to install the floating-point...
fexecve
execute a file
fflush
If stream points to an output stream or an update stream in which the most recent operation was not input, fflush() shall cause any unwritten data for that...
ffs
The ffs() function shall find the first bit set (beginning with the least significant bit) in i, and return the index of that bit. Bits are numbered starting at...
fgetc
If the end-of-file indicator for the input stream pointed to by stream is not set and a next byte is present, the fgetc() function shall obtain the next byte as...
fgetpos
The fgetpos() function shall store the current values of the parse state (if any) and file position indicator for the stream pointed to by stream in the object...
fgets
The fgets() function shall read bytes from stream into the array pointed to by s, until n-1 bytes are read, or a <newline> is read and transferred to s, or an...
fgetwc
The fgetwc() function shall obtain the next character (if present) from the input stream pointed to by stream, convert that to the corresponding wide-character...
fgetws
The fgetws() function shall read characters from the stream, convert these to the corresponding wide-character codes, place them in the wchar_t array pointed to...
fileno
The fileno() function shall return the integer file descriptor associated with the stream pointed to by stream.
flockfile
These functions shall provide for explicit application-level locking of stdio (FILE *) objects. These functions can be used by a thread to delineate a sequence...
floor
These functions shall compute the largest integral value not greater than x.
fma
These functions shall compute (x * y) + z, rounded as one ternary operation: they shall compute the value (as if) to infinite precision and round once to the...
fmax
These functions shall determine the maximum numeric value of their arguments. NaN arguments shall be treated as missing data: if one argument is a NaN and the...
fmemopen
The fmemopen() function shall associate the buffer given by the buf and size arguments with a stream. The buf argument shall be either a null pointer or point...
fmin
These functions shall determine the minimum numeric value of their arguments. NaN arguments shall be treated as missing data: if one argument is a NaN and the...
fmod
These functions shall return the floating-point remainder of the division of x by y. An application wishing to check for error situations should set errno to...
fmtmsg
The fmtmsg() function shall display messages in a specified format instead of the traditional printf() function. Based on a message's classification component...
fnmatch
The fnmatch() function shall match patterns as described in the Shell and Utilities volume of POSIX.1‐2008, Section 2.13.1, Patterns Matching a Single Character...
fopen
The fopen() function shall open the file whose pathname is the string pointed to by pathname, and associates a stream with it. The mode argument points to a...
fork
The fork() function shall create a new process.
fpathconf
The fpathconf() and pathconf() functions shall determine the current value of a configurable limit or option (variable) that is associated with a file or...
fpclassify
The fpclassify() macro shall classify its argument value as NaN, infinite, normal, subnormal, zero, or into another implementation-defined category. First, an...
fprintf
Excluding dprintf(): The fprintf() function shall place output on the named output stream. The printf() function shall place output on the standard output...
fputc
The fputc() function shall write the byte specified by c (converted to an unsigned char) to the output stream pointed to by stream, at the position indicated by...
fputs
The fputs() function shall write the null-terminated string pointed to by s to the stream pointed to by stream. The terminating null byte shall not be written...
fputwc
The fputwc() function shall write the character corresponding to the wide-character code wc to the output stream pointed to by stream, at the position indicated...
fputws
The fputws() function shall write a character string corresponding to the (null-terminated) wide-character string pointed to by ws to the stream pointed to by...
fread
The fread() function shall read into the array pointed to by ptr up to nitems elements whose size is specified by size in bytes, from the stream pointed to by...
free
The free() function shall cause the space pointed to by ptr to be deallocated; that is, made available for further allocation. If ptr is a null pointer, no...
freeaddrinfo
The freeaddrinfo() function shall free one or more addrinfo structures returned by getaddrinfo(), along with any additional storage associated with those...
freelocale
The freelocale() function shall cause the resources allocated for a locale object returned by a call to the newlocale() or duplocale() functions to be released...
freopen
The freopen() function shall first attempt to flush the stream associated with stream as if by a call to fflush(stream). Failure to flush the stream...
frexp
These functions shall break a floating-point number num into a normalized fraction and an integral power of 2. The integer exponent shall be stored in the int...
fscanf
The fscanf() function shall read from the named input stream. The scanf() function shall read from the standard input stream stdin. The sscanf() function shall...
fseek
The fseek() function shall set the file-position indicator for the stream pointed to by stream. If a read or write error occurs, the error indicator for the...
fsetpos
The fsetpos() function shall set the file position and state indicators for the stream pointed to by stream according to the value of the object pointed to by...
fstat
The fstat() function shall obtain information about an open file associated with the file descriptor fildes, and shall write it to the area pointed to by buf...
fstatat
The stat() function shall obtain information about the named file and write it to the area pointed to by the buf argument. The path argument points to a...
fstatvfs
The fstatvfs() function shall obtain information about the file system containing the file referenced by fildes. The statvfs() function shall obtain information...
fsync
The fsync() function shall request that all data for the open file descriptor named by fildes is to be transferred to the storage device associated with the...
ftell
The ftell() function shall obtain the current value of the file-position indicator for the stream pointed to by stream. The ftell() function shall not change...
ftok
The ftok() function shall return a key based on path and id that is usable in subsequent calls to msgget(), semget(), and shmget(). The application shall ensure...
ftruncate
If fildes is not a valid file descriptor open for writing, the ftruncate() function shall fail. If fildes refers to a regular file, the ftruncate() function...
ftrylockfile
stdio locking functions
ftw
The ftw() function shall recursively descend the directory hierarchy rooted in path. For each object in the hierarchy, ftw() shall call the function pointed to...
funlockfile
stdio locking functions
futimens
The futimens() and utimensat() functions shall set the access and modification times of a file to the values of the times argument. The futimens() function...
fwide
The fwide() function shall determine the orientation of the stream pointed to by stream. If mode is greater than zero, the function first attempts to make the...
fwprintf
The fwprintf() function shall place output on the named output stream. The wprintf() function shall place output on the standard output stream stdout. The...
fwrite
The fwrite() function shall write, from the array pointed to by ptr, up to nitems elements whose size is specified by size, to the stream pointed to by stream...
fwscanf
The fwscanf() function shall read from the named input stream. The wscanf() function shall read from the standard input stream stdin. The swscanf() function...
gai_strerror
The gai_strerror() function shall return a text string describing an error value for the getaddrinfo() and getnameinfo() functions listed in the <netdb.h>...
getaddrinfo
get address information
getc
The getc() function shall be equivalent to fgetc(), except that if it is implemented as a macro it may evaluate stream more than once, so the argument should...
getchar
The getchar() function shall be equivalent to getc(stdin).
getchar_unlocked
Refer to getc_unlocked().
getc_unlocked
Versions of the functions getc(), getchar(), putc(), and putchar() respectively named getc_unlocked(), getchar_unlocked(), putc_unlocked(), and...
getcwd
The getcwd() function shall place an absolute pathname of the current working directory in the array pointed to by buf, and return buf. The pathname shall...
getdate
The getdate() function shall convert a string representation of a date or time into a broken-down time. The external variable or macro getdate_err, which has...
getdelim
The getdelim() function shall read from stream until it encounters a character matching the delimiter character. The delimiter argument is an int, the value of...
getegid
The getegid() function shall return the effective group ID of the calling process.
getenv
The getenv() function shall search the environment of the calling process (see the Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment Variables)...
geteuid
The geteuid() function shall return the effective user ID of the calling process.
getgid
The getgid() function shall return the real group ID of the calling process.
getgrent
get the group database entry
getgrgid
The getgrgid() function shall search the group database for an entry with a matching gid. The getgrgid() function need not be thread-safe. The getgrgid_r()...
getgrnam
The getgrnam() function shall search the group database for an entry with a matching name. The getgrnam() function need not be thread-safe. The getgrnam_r()...
getgroups
The getgroups() function shall fill in the array grouplist with the current supplementary group IDs of the calling process. It is implementation-defined whether...
gethostent
network host database functions
gethostid
The gethostid() function shall retrieve a 32-bit identifier for the current host.
gethostname
The gethostname() function shall return the standard host name for the current machine. The namelen argument shall specify the size of the array pointed to by...
getitimer
The getitimer() function shall store the current value of the timer specified by which into the structure pointed to by value. The setitimer() function shall...
getline
read a delimited record from stream
getlogin
The getlogin() function shall return a pointer to a string containing the user name associated by the login activity with the controlling terminal of the...
getmsg
The getmsg() function shall retrieve the contents of a message located at the head of the STREAM head read queue associated with a STREAMS file and place the...
getnameinfo
The getnameinfo() function shall translate a socket address to a node name and service location, all of which are defined as in freeaddrinfo(). The sa argument...
getnetbyaddr
network database functions
getopt
The getopt() function is a command-line parser that shall follow Utility Syntax Guidelines 3, 4, 5, 6, 7, 9, and 10 in the Base Definitions volume of...
getpeername
The getpeername() function shall retrieve the peer address of the specified socket, store this address in the sockaddr structure pointed to by the address...
getpgid
The getpgid() function shall return the process group ID of the process whose process ID is equal to pid. If pid is equal to 0, getpgid() shall return the...
getpgrp
The getpgrp() function shall return the process group ID of the calling process.
getpid
The getpid() function shall return the process ID of the calling process.
getpmsg
receive next message from a STREAMS file
getppid
The getppid() function shall return the parent process ID of the calling process.
getpriority
The getpriority() function shall obtain the nice value of a process, process group, or user. The setpriority() function shall set the nice value of a process...
getprotobyname
network protocol database functions
getpwent
get user database entry
getpwnam
The getpwnam() function shall search the user database for an entry with a matching name. The getpwnam() function need not be thread-safe. Applications wishing...
getpwuid
The getpwuid() function shall search the user database for an entry with a matching uid. The getpwuid() function need not be thread-safe. Applications wishing...
getrlimit
The getrlimit() function shall get, and the setrlimit() function shall set, limits on the consumption of a variety of resources. Each call to either getrlimit()...
getrusage
The getrusage() function shall provide measures of the resources used by the current process or its terminated and waited-for child processes. If the value of...
gets
The gets() function shall read bytes from the standard input stream, stdin, into the array pointed to by s, until a <newline> is read or an end-of-file...
getservbyname
network services database functions
getsid
The getsid() function shall obtain the process group ID of the process that is the session leader of the process specified by pid. If pid is (pid_t)0, it...
getsockname
The getsockname() function shall retrieve the locally-bound name of the specified socket, store this address in the sockaddr structure pointed to by the address...
getsockopt
The getsockopt() function manipulates options associated with a socket. The getsockopt() function shall retrieve the value for the option specified by the...
getsubopt
The getsubopt() function shall parse suboption arguments in a flag argument. Such options often result from the use of getopt(). The getsubopt() argument...
gettimeofday
The gettimeofday() function shall obtain the current time, expressed as seconds and microseconds since the Epoch, and store it in the timeval structure pointed...
getuid
The getuid() function shall return the real user ID of the calling process.
getutxent
get user accounting database entries
getwc
The getwc() function shall be equivalent to fgetwc(), except that if it is implemented as a macro it may evaluate stream more than once, so the argument should...
getwchar
The getwchar() function shall be equivalent to getwc(stdin).
glob
The glob() function is a pathname generator that shall implement the rules defined in the Shell and Utilities volume of POSIX.1‐2008, Section 2.13, Pattern...
gmtime
For gmtime(): The gmtime() function shall convert the time in seconds since the Epoch pointed to by timer into a broken-down time, expressed as Coordinated...
grantpt
The grantpt() function shall change the mode and ownership of the slave pseudo-terminal device associated with its master pseudo-terminal counterpart. The...
hcreate
The hcreate(), hdestroy(), and hsearch() functions shall manage hash search tables. The hcreate() function shall allocate sufficient space for the table, and...
htonl
These functions shall convert 16-bit and 32-bit quantities between network byte order and host byte order. On some implementations, these functions are defined...
hypot
These functions shall compute the value of the square root of x2+y2 without undue overflow or underflow. An application wishing to check for error situations...
iconv
The iconv() function shall convert the sequence of characters from one codeset, in the array specified by inbuf, into a sequence of corresponding characters in...
iconv_close
The iconv_close() function shall deallocate the conversion descriptor cd and all other associated resources allocated by iconv_open(). If a file descriptor is...
iconv_open
The iconv_open() function shall return a conversion descriptor that describes a conversion from the codeset specified by the string pointed to by the fromcode...
if_freenameindex
The if_freenameindex() function shall free the memory allocated by if_nameindex(). The ptr argument shall be a pointer that was returned by if_nameindex()...
if_indextoname
The if_indextoname() function shall map an interface index to its corresponding name. When this function is called, ifname shall point to a buffer of at least...
if_nameindex
The if_nameindex() function shall return an array of if_nameindex structures, one structure per interface. The end of the array is indicated by a structure with...
if_nametoindex
The if_nametoindex() function shall return the interface index corresponding to name ifname.
ilogb
These functions shall return the exponent part of their argument x. Formally, the return value is the integral part of logr|x| as a signed integral value, for...
imaxabs
The imaxabs() function shall compute the absolute value of an integer j. If the result cannot be represented, the behavior is undefined.
imaxdiv
The imaxdiv() function shall compute numer / denom and numer % denom in a single operation.
inet_addr
The inet_addr() function shall convert the string pointed to by cp, in the standard IPv4 dotted decimal notation, to an integer value suitable for use as an...
inet_ntop
The inet_ntop() function shall convert a numeric address into a text string suitable for presentation. The af argument shall specify the family of the address...
initstate
The random() function shall use a non-linear additive feedback random-number generator employing a default state array size of 31 long integers to return...
insque
The insque() and remque() functions shall manipulate queues built from doubly-linked lists. The queue can be either circular or linear. An application using...
ioctl
The ioctl() function shall perform a variety of control functions on STREAMS devices. For non-STREAMS devices, the functions performed by this call are...
isalnum
For isalnum(): The isalnum() and isalnum_l() functions shall test whether c is a character of class alpha or digit in the current locale, or in the locale...
isalpha
For isalpha(): The isalpha() and isalpha_l() functions shall test whether c is a character of class alpha in the current locale, or in the locale represented by...
isascii
The isascii() function shall test whether c is a 7-bit US-ASCII character code. The isascii() function is defined on all integer values.
isastream
The isastream() function shall test whether fildes, an open file descriptor, is associated with a STREAMS-based file.
isatty
The isatty() function shall test whether fildes, an open file descriptor, is associated with a terminal device.
isblank
For isblank(): The isblank() and isblank_l() functions shall test whether c is a character of class blank in the current locale, or in the locale represented by...
iscntrl
For iscntrl(): The iscntrl() and iscntrl_l() functions shall test whether c is a character of class cntrl in the current locale, or in the locale represented by...
isdigit
For isdigit(): The isdigit() and isdigit_l() functions shall test whether c is a character of class digit in the current locale, or in the locale represented by...
isfinite
The isfinite() macro shall determine whether its argument has a finite value (zero, subnormal, or normal, and not infinite or NaN). First, an argument...
isgraph
For isgraph(): The isgraph() and isgraph_l() functions shall test whether c is a character of class graph in the current locale, or in the locale represented by...
isgreater
The isgreater() macro shall determine whether its first argument is greater than its second argument. The value of isgreater(x, y) shall be equal to (x) > (y)...
isgreaterequal
The isgreaterequal() macro shall determine whether its first argument is greater than or equal to its second argument. The value of isgreaterequal(x, y) shall...
isinf
The isinf() macro shall determine whether its argument value is an infinity (positive or negative). First, an argument represented in a format wider than its...
isless
The isless() macro shall determine whether its first argument is less than its second argument. The value of isless(x, y) shall be equal to (x) < (y); however...
islessequal
The islessequal() macro shall determine whether its first argument is less than or equal to its second argument. The value of islessequal(x, y) shall be equal...
islessgreater
The islessgreater() macro shall determine whether its first argument is less than or greater than its second argument. The islessgreater(x, y) macro is similar...
islower
For islower(): The islower() and islower_l() functions shall test whether c is a character of class lower in the current locale, or in the locale represented by...
isnan
The isnan() macro shall determine whether its argument value is a NaN. First, an argument represented in a format wider than its semantic type is converted to...
isnormal
The isnormal() macro shall determine whether its argument value is normal (neither zero, subnormal, infinite, nor NaN). First, an argument represented in a...
isprint
For isprint(): The isprint() and isprint_l() functions shall test whether c is a character of class print in the current locale, or in the locale represented by...
ispunct
For ispunct(): The ispunct() and ispunct_l() functions shall test whether c is a character of class punct in the current locale, or in the locale represented by...
isspace
For isspace(): The isspace() and isspace_l() functions shall test whether c is a character of class space in the current locale, or in the locale represented by...
isunordered
The isunordered() macro shall determine whether its arguments are unordered.
isupper
For isupper(): The isupper() and isupper_l() functions shall test whether c is a character of class upper in the current locale, or in the locale represented by...
iswalnum
For iswalnum(): The iswalnum() and iswalnum_l() functions shall test whether wc is a wide-character code representing a character of class alpha or digit in the...
iswalpha
For iswalpha(): The iswalpha() and iswalpha_l() functions shall test whether wc is a wide-character code representing a character of class alpha in the current...
iswblank
For iswblank(): The iswblank() and iswblank() functions shall test whether wc is a wide-character code representing a character of class blank in the current...
iswcntrl
For iswcntrl(): The iswcntrl() and iswcntrl_l() functions shall test whether wc is a wide-character code representing a character of class cntrl in the current...
iswctype
For iswctype(): The iswctype() and iswctype_l() functions shall determine whether the wide-character code wc has the character class charclass, returning true...
iswdigit
For iswdigit(): The iswdigit() and iswdigit_l() functions shall test whether wc is a wide-character code representing a character of class digit in the current...
iswgraph
For iswgraph(): The iswgraph() and iswgraph_l() functions shall test whether wc is a wide-character code representing a character of class graph in the current...
iswlower
For iswlower(): The iswlower() and iswlower_l() functions shall test whether wc is a wide-character code representing a character of class lower in the current...
iswprint
For iswprint(): The iswprint() and iswprint_l() functions shall test whether wc is a wide-character code representing a character of class print in the current...
iswpunct
For iswpunct(): The iswpunct() and iswpunct_l() functions shall test whether wc is a wide-character code representing a character of class punct in the current...
iswspace
For iswspace(): The iswspace() and iswspace_l() functions shall test whether wc is a wide-character code representing a character of class space in the current...
iswupper
For iswupper(): The iswupper() and iswupper_l() functions shall test whether wc is a wide-character code representing a character of class upper in the current...
iswxdigit
For iswxdigit(): The iswxdigit() and iswxdigit_l() functions shall test whether wc is a wide-character code representing a character of class xdigit in the...
isxdigit
For isxdigit(): The isxdigit() and isxdigit_l() functions shall test whether c is a character of class xdigit in the current locale, or in the locale...
j0
The j0(), j1(), and jn() functions shall compute Bessel functions of x of the first kind of orders 0, 1, and n, respectively. An application wishing to check...
jrand48
generate a uniformly distributed pseudo-random long signed integer
kill
The kill() function shall send a signal to a process or a group of processes specified by pid. The signal to be sent is specified by sig and is either one from...
killpg
The killpg() function shall send the signal specified by sig to the process group specified by pgrp. If pgrp is greater than 1, killpg(pgrp, sig) shall be...
l64a
convert a 32-bit integer to a radix-64 ASCII string
labs
The labs() function shall compute the absolute value of the long integer operand i. The llabs() function shall compute the absolute value of the long long...
lchown
The lchown() function shall be equivalent to chown(), except in the case where the named file is a symbolic link. In this case, lchown() shall change the...
lcong48
seed a uniformly distributed pseudo-random signed long integer generator
ldexp
These functions shall compute the quantity x * 2exp. An application wishing to check for error situations should set errno to zero and call...
ldiv
These functions shall compute the quotient and remainder of the division of the numerator numer by the denominator denom. If the division is inexact, the...
lfind
find entry in a linear search table
lgamma
These functions shall compute log_e&boxv;Γ(x)&boxv; where Γ(x) is defined as ∫0∞e^-tt^x-1dt. The argument x need not be a non-positive integer (Γ(x) is defined...
link
The link() function shall create a new link (directory entry) for the existing file, path1. The path1 argument points to a pathname naming an existing file. The...
lio_listio
The lio_listio() function shall initiate a list of I/O requests with a single function call. The mode argument takes one of the values LIO_WAIT or LIO_NOWAIT...
listen
The listen() function shall mark a connection-mode socket, specified by the socket argument, as accepting connections. The backlog argument provides a hint to...
llabs
return a long integer absolute value
lldiv
compute quotient and remainder of a long division
llrint
These functions shall round their argument to the nearest integer value, rounding according to the current rounding direction. An application wishing to check...
llround
These functions shall round their argument to the nearest integer value, rounding halfway cases away from zero, regardless of the current rounding direction. An...
localeconv
The localeconv() function shall set the components of an object with the type struct lconv with the values appropriate for the formatting of numeric quantities...
localtime
For localtime(): The localtime() function shall convert the time in seconds since the Epoch pointed to by timer into a broken-down time, expressed as a local...
lockf
The lockf() function shall lock sections of a file with advisory-mode locks. Calls to lockf() from threads in other processes which attempt to lock the locked...
log
These functions shall compute the natural logarithm of their argument x, loge(x). An application wishing to check for error situations should set errno to zero...
log10
These functions shall compute the base 10 logarithm of their argument x, log10(x). An application wishing to check for error situations should set errno to zero...
log1p
These functions shall compute loge(1.0 + x). An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)...
log2
These functions shall compute the base 2 logarithm of their argument x, log2(x). An application wishing to check for error situations should set errno to zero...
logb
These functions shall compute the exponent of x, which is the integral part of logr |x|, as a signed floating-point value, for non-zero x, where r is the radix...
logf
natural logarithm function
longjmp
The longjmp() function shall restore the environment saved by the most recent invocation of setjmp() in the same process, with the corresponding jmp_buf...
_longjmp
The _longjmp() and _setjmp() functions shall be equivalent to longjmp() and setjmp(), respectively, with the additional restriction that _longjmp() and...
lrand48
generate uniformly distributed pseudo-random non-negative long integers
lrint
These functions shall round their argument to the nearest integer value, rounding according to the current rounding direction. An application wishing to check...
lround
These functions shall round their argument to the nearest integer value, rounding halfway cases away from zero, regardless of the current rounding direction. An...
lsearch
The lsearch() function shall linearly search the table and return a pointer into the table for the matching entry. If the entry does not occur, it shall be...
lseek
move the read/write file offset
lstat
get file status
malloc
The malloc() function shall allocate unused space for an object whose size in bytes is specified by size and whose value is unspecified. The order and...
mblen
If s is not a null pointer, mblen() shall determine the number of bytes constituting the character pointed to by s.
mbrlen
If s is not a null pointer, mbrlen() shall determine the number of bytes constituting the character pointed to by s.
mbrtowc
convert a character to a wide-character code (restartable)
mbsinit
If ps is not a null pointer, the mbsinit() function shall determine whether the object pointed to by ps describes an initial conversion state.
mbsrtowcs
For mbsrtowcs(): The mbsrtowcs() function shall convert a sequence of characters, beginning in the conversion state described by the object pointed to by ps...
mbstowcs
The mbstowcs() function shall convert a sequence of characters that begins in the initial shift state from the array pointed to by s into a sequence of...
mbtowc
If s is not a null pointer, mbtowc() shall determine the number of bytes that constitute the character pointed to by s. It shall then determine the...
memccpy
The memccpy() function shall copy bytes from memory area s2 into s1, stopping after the first occurrence of byte c (converted to an unsigned char) is copied, or...
memchr
The memchr() function shall locate the first occurrence of c (converted to an unsigned char) in the initial n bytes (each interpreted as unsigned char) pointed...
memcmp
The memcmp() function shall compare the first n bytes (each interpreted as unsigned char) of the object pointed to by s1 to the first n bytes of the object...
memcpy
The memcpy() function shall copy n bytes from the object pointed to by s2 into the object pointed to by s1. If copying takes place between objects that overlap...
memmove
The memmove() function shall copy n bytes from the object pointed to by s2 into the object pointed to by s1. Copying takes place as if the n bytes from the...
memset
The memset() function shall copy c (converted to an unsigned char) into each of the first n bytes of the object pointed to by s.
mkdir
The mkdir() function shall create a new directory with name path. The file permission bits of the new directory shall be initialized from mode. These file...
mkdtemp
The mkdtemp() function uses the contents of template to construct a unique directory name. The string provided in template shall be a pathname ending with six...
mkfifo
The mkfifo() function shall create a new FIFO special file named by the pathname pointed to by path. The file permission bits of the new FIFO shall be...
mknod
The mknod() function shall create a new file named by the pathname to which the argument path points.
mkstemp
create a unique directory
mktime
The mktime() function shall convert the broken-down time, expressed as local time, in the structure pointed to by timeptr, into a time since the Epoch value...
mlock
The mlock() function shall cause those whole pages containing any part of the address space of the process starting at address addr and continuing for len bytes...
mlockall
The mlockall() function shall cause all of the pages mapped by the address space of a process to be memory-resident until unlocked or until the process exits or...
mmap
The mmap() function shall establish a mapping between an address space of a process and a memory object.
modf
These functions shall break the argument x into integral and fractional parts, each of which has the same sign as the argument. It stores the integral part as a...
mprotect
The mprotect() function shall change the access protections to be that specified by prot for those whole pages containing any part of the address space of the...
mq_close
The mq_close() function shall remove the association between the message queue descriptor, mqdes, and its message queue. The results of using this message queue...
mq_getattr
The mq_getattr() function shall obtain status information and attributes of the message queue and the open message queue description associated with the message...
mq_notify
If the argument notification is not NULL, this function shall register the calling process to be notified of message arrival at an empty message queue...
mq_open
The mq_open() function shall establish the connection between a process and a message queue with a message queue descriptor. It shall create an open message...
mq_receive
The mq_receive() function shall receive the oldest of the highest priority message(s) from the message queue specified by mqdes. If the size of the buffer in...
mq_send
The mq_send() function shall add the message pointed to by the argument msg_ptr to the message queue specified by mqdes. The msg_len argument specifies the...
mq_setattr
The mq_setattr() function shall set attributes associated with the open message queue description referenced by the message queue descriptor specified by mqdes.
mq_timedreceive
receive a message from a message queue (ADVANCED REALTIME)
mq_timedsend
send a message to a message queue (ADVANCED REALTIME)
mq_unlink
The mq_unlink() function shall remove the message queue named by the string name. If one or more processes have the message queue open when mq_unlink() is...
mrand48
generate uniformly distributed pseudo-random signed long integers
msgctl
The msgctl() function operates on XSI message queues (see the Base Definitions volume of POSIX.1‐2008, Section 3.225, Message Queue). It is unspecified whether...
msgget
The msgget() function operates on XSI message queues (see the Base Definitions volume of POSIX.1‐2008, Section 3.225, Message Queue). It is unspecified whether...
msgrcv
The msgrcv() function operates on XSI message queues (see the Base Definitions volume of POSIX.1‐2008, Section 3.225, Message Queue). It is unspecified whether...
msgsnd
The msgsnd() function operates on XSI message queues (see the Base Definitions volume of POSIX.1‐2008, Section 3.225, Message Queue). It is unspecified whether...
msync
The msync() function shall write all modified data to permanent storage locations, if any, in those whole pages containing any part of the address space of the...
munlock
unlock a range of process address space
munlockall
unlock the address space of a process
munmap
The munmap() function shall remove any mappings for those entire pages containing any part of the address space of the process starting at addr and continuing...
nan
return quiet NaN
nanosleep
The nanosleep() function shall cause the current thread to be suspended from execution until either the time interval specified by the rqtp argument has elapsed...
nearbyint
These functions shall round their argument to an integer value in floating-point format, using the current rounding direction and without raising the inexact...
newlocale
The newlocale() function shall create a new locale object or modify an existing one. If the base argument is (locale_t)0, a new locale object shall be created...
nextafter
The nextafter(), nextafterf(), and nextafterl() functions shall compute the next representable floating-point value following x in the direction of y. Thus, if...
nftw
The nftw() function shall recursively descend the directory hierarchy rooted in path.
nice
The nice() function shall add the value of incr to the nice value of the calling process. A nice value of a process is a non-negative number for which a more...
nl_langinfo
The nl_langinfo() and nl_langinfo_l() functions shall return a pointer to a string containing information relevant to the particular language or cultural area...
nrand48
generate uniformly distributed pseudo-random non-negative long integers
ntohl
convert values between host and network byte order
open
The open() function shall establish the connection between a file and a file descriptor. It shall create an open file description that refers to a file and a...
openat
open file relative to directory file descriptor
opendir
open directory associated with file descriptor
openlog
open a connection to the logging facility
open_memstream
The open_memstream() and open_wmemstream() functions shall create an I/O stream associated with a dynamically allocated memory buffer. The stream shall be...
optarg
options parsing variables
pathconf
get configurable pathname variables
pause
The pause() function shall suspend the calling thread until delivery of a signal whose action is either to execute a signal-catching function or to terminate...
pclose
The pclose() function shall close a stream that was opened by popen(), wait for the command to terminate, and return the termination status of the process that...
perror
write error messages to standard error
pipe
The pipe() function shall create a pipe and place two file descriptors, one each into the arguments fildes[0] and fildes[1], that refer to the open file...
poll
The poll() function provides applications with a mechanism for multiplexing input/output over a set of file descriptors. For each member of the array pointed to...
popen
The popen() function shall execute the command specified by the string command. It shall create a pipe between the calling program and the executed command, and...
posix_fadvise
The posix_fadvise() function shall advise the implementation on the expected behavior of the application with respect to the data in the file associated with...
posix_fallocate
The posix_fallocate() function shall ensure that any required storage for regular file data starting at offset and continuing for len bytes is allocated on the...
posix_madvise
The posix_madvise() function shall advise the implementation on the expected behavior of the application with respect to the data in the memory starting at...
posix_memalign
The posix_memalign() function shall allocate size bytes aligned on a boundary specified by alignment, and shall return a pointer to the allocated memory in...
posix_mem_offset
The posix_mem_offset() function shall return in the variable pointed to by off a value that identifies the offset (or location), within a memory object, of the...
posix_openpt
The posix_openpt() function shall establish a connection between a master device for a pseudo-terminal and a file descriptor. The file descriptor is used by...
posix_spawn
The posix_spawn() and posix_spawnp() functions shall create a new process (child process) from the specified process image. The new process image shall be...
posix_spawnattr_destroy
The posix_spawnattr_destroy() function shall destroy a spawn attributes object. A destroyed attr attributes object can be reinitialized using...
posix_spawnattr_getflags
The posix_spawnattr_getflags() function shall obtain the value of the spawn-flags attribute from the attributes object referenced by attr. The...
posix_spawnattr_getpgroup
The posix_spawnattr_getpgroup() function shall obtain the value of the spawn-pgroup attribute from the attributes object referenced by attr. The...
posix_spawnattr_getschedparam
The posix_spawnattr_getschedparam() function shall obtain the value of the spawn-schedparam attribute from the attributes object referenced by attr. The...
posix_spawnattr_getschedpolicy
The posix_spawnattr_getschedpolicy() function shall obtain the value of the spawn-schedpolicy attribute from the attributes object referenced by attr. The...
posix_spawnattr_getsigdefault
The posix_spawnattr_getsigdefault() function shall obtain the value of the spawn-sigdefault attribute from the attributes object referenced by attr. The...
posix_spawnattr_getsigmask
The posix_spawnattr_getsigmask() function shall obtain the value of the spawn-sigmask attribute from the attributes object referenced by attr. The...
posix_spawnattr_init
Refer to posix_spawnattr_destroy().
posix_spawnattr_setflags
Refer to posix_spawnattr_getflags().
posix_spawnattr_setpgroup
Refer to posix_spawnattr_getpgroup().
posix_spawnattr_setschedparam
Refer to posix_spawnattr_getschedparam().
posix_spawnattr_setschedpolicy
Refer to posix_spawnattr_getschedpolicy().
posix_spawnattr_setsigdefault
Refer to posix_spawnattr_getsigdefault().
posix_spawnattr_setsigmask
Refer to posix_spawnattr_getsigmask().
posix_spawn_file_actions_addclose
These functions shall add or delete a close or open action to a spawn file actions object. A spawn file actions object is of type posix_spawn_file_actions_t...
posix_spawn_file_actions_adddup2
The posix_spawn_file_actions_adddup2() function shall add a dup2() action to the object referenced by file_actions that shall cause the file descriptor fildes...
posix_spawn_file_actions_addopen
Refer to posix_spawn_file_actions_addclose().
posix_spawn_file_actions_destroy
The posix_spawn_file_actions_destroy() function shall destroy the object referenced by file_actions; the object becomes, in effect, uninitialized. An...
posix_spawnp
spawn a process (ADVANCED REALTIME)
posix_trace_attr_destroy
The posix_trace_attr_destroy() function shall destroy an initialized trace attributes object. A destroyed attr attributes object can be reinitialized using...
posix_trace_attr_getclockres
The posix_trace_attr_getclockres() function shall copy the clock resolution of the clock used to generate timestamps from the clock-resolution attribute of the...
posix_trace_attr_getinherited
The posix_trace_attr_getinherited() and posix_trace_attr_setinherited() functions, respectively, shall get and set the inheritance policy stored in the...
posix_trace_attr_getlogsize
The posix_trace_attr_getlogsize() function shall copy the log size, in bytes, from the log-max-size attribute of the attributes object pointed to by the attr...
posix_trace_attr_getname
Refer to posix_trace_attr_getclockres().
posix_trace_attr_getstreamfullpolicy
Refer to posix_trace_attr_getinherited().
posix_trace_attr_getstreamsize
Refer to posix_trace_attr_getlogsize().
posix_trace_attr_init
Refer to posix_trace_attr_destroy().
posix_trace_attr_setinherited
Refer to posix_trace_attr_getinherited().
posix_trace_attr_setlogsize
Refer to posix_trace_attr_getlogsize().
posix_trace_attr_setname
Refer to posix_trace_attr_getclockres().
posix_trace_attr_setstreamfullpolicy
Refer to posix_trace_attr_getinherited().
posix_trace_attr_setstreamsize
Refer to posix_trace_attr_getlogsize().
posix_trace_clear
The posix_trace_clear() function shall reinitialize the trace stream identified by the argument trid as if it were returning from the posix_trace_create()...
posix_trace_close
The posix_trace_close() function shall deallocate the trace log identifier indicated by trid, and all of its associated resources. If there is no valid trace...
posix_trace_create
The posix_trace_create() function shall create an active trace stream. It allocates all the resources needed by the trace stream being created for tracing the...
posix_trace_event
The posix_trace_event() function shall record the event_id and the user data pointed to by data_ptr in the trace stream into which the calling process is being...
posix_trace_eventid_equal
The posix_trace_eventid_equal() function shall compare the trace event type identifiers event1 and event2 from the same trace stream or the same trace log...
posix_trace_eventid_open
Refer to posix_trace_event().
posix_trace_eventset_add
These primitives manipulate sets of trace event types. They operate on data objects addressable by the application, not on the current trace event filter of any...
posix_trace_eventtypelist_getnext_id
The first time posix_trace_eventtypelist_getnext_id() is called, the function shall return in the variable pointed to by event the first trace event type...
posix_trace_flush
Refer to posix_trace_create().
posix_trace_get_attr
The posix_trace_get_attr() function shall copy the attributes of the active trace stream identified by trid into the object pointed to by the attr argument. If...
posix_trace_get_filter
The posix_trace_get_filter() function shall retrieve, into the argument pointed to by set, the actual trace event filter from the trace stream specified by...
posix_trace_getnext_event
The posix_trace_getnext_event() function shall report a recorded trace event either from an active trace stream without log or a pre-recorded trace stream...
posix_trace_get_status
Refer to posix_trace_get_attr().
posix_trace_open
Refer to posix_trace_close().
posix_trace_set_filter
Refer to posix_trace_get_filter().
posix_trace_shutdown
Refer to posix_trace_create().
posix_trace_start
The posix_trace_start() and posix_trace_stop() functions, respectively, shall start and stop the trace stream identified by the argument trid. The effect of...
posix_trace_timedgetnext_event
Refer to posix_trace_getnext_event().
posix_trace_trid_eventid_open
Refer to posix_trace_eventid_equal().
posix_trace_trygetnext_event
Refer to posix_trace_getnext_event().
posix_typed_mem_get_info
The posix_typed_mem_get_info() function shall return, in the posix_tmi_length field of the posix_typed_mem_info structure pointed to by info, the maximum length...
posix_typed_mem_open
The posix_typed_mem_open() function shall establish a connection between the typed memory object specified by the string pointed to by name and a file...
pow
These functions shall compute the value of x raised to the power y, xy. If x is negative, the application shall ensure that y is an integer value. An...
pread
read from a file
printf
print formatted output
pselect
The pselect() function shall examine the file descriptor sets whose addresses are passed in the readfds, writefds, and errorfds parameters to see whether some...
psiginfo
The psiginfo() and psignal() functions shall print a message out on stderr associated with a signal number. If message is not null and is not the empty string...
pthread_atfork
The pthread_atfork() function shall declare fork handlers to be called before and after fork(), in the context of the thread that called fork(). The prepare...
pthread_attr_destroy
The pthread_attr_destroy() function shall destroy a thread attributes object. An implementation may cause pthread_attr_destroy() to set attr to an...
pthread_attr_getdetachstate
The detachstate attribute controls whether the thread is created in a detached state. If the thread is created detached, then use of the ID of the newly created...
pthread_attr_getguardsize
The pthread_attr_getguardsize() function shall get the guardsize attribute in the attr object. This attribute shall be returned in the guardsize parameter. The...
pthread_attr_getinheritsched
The pthread_attr_getinheritsched() and pthread_attr_setinheritsched() functions, respectively, shall get and set the inheritsched attribute in the attr...
pthread_attr_getschedparam
The pthread_attr_getschedparam() and pthread_attr_setschedparam() functions, respectively, shall get and set the scheduling parameter attributes in the attr...
pthread_attr_getschedpolicy
The pthread_attr_getschedpolicy() and pthread_attr_setschedpolicy() functions, respectively, shall get and set the schedpolicy attribute in the attr argument...
pthread_attr_getscope
The pthread_attr_getscope() and pthread_attr_setscope() functions, respectively, shall get and set the contentionscope attribute in the attr object. The...
pthread_attr_getstack
The pthread_attr_getstack() and pthread_attr_setstack() functions, respectively, shall get and set the thread creation stack attributes stackaddr and stacksize...
pthread_attr_getstacksize
The pthread_attr_getstacksize() and pthread_attr_setstacksize() functions, respectively, shall get and set the thread creation stacksize attribute in the attr...
pthread_attr_init
Refer to pthread_attr_destroy().
pthread_attr_setdetachstate
Refer to pthread_attr_getdetachstate().
pthread_attr_setguardsize
Refer to pthread_attr_getguardsize().
pthread_attr_setinheritsched
Refer to pthread_attr_getinheritsched().
pthread_attr_setschedparam
Refer to pthread_attr_getschedparam().
pthread_attr_setschedpolicy
Refer to pthread_attr_getschedpolicy().
pthread_attr_setscope
Refer to pthread_attr_getscope().
pthread_attr_setstack
Refer to pthread_attr_getstack().
pthread_attr_setstacksize
Refer to pthread_attr_getstacksize().
pthread_barrierattr_destroy
The pthread_barrierattr_destroy() function shall destroy a barrier attributes object. A destroyed attr attributes object can be reinitialized using...
pthread_barrierattr_getpshared
The pthread_barrierattr_getpshared() function shall obtain the value of the process-shared attribute from the attributes object referenced by attr. The...
pthread_barrierattr_init
Refer to pthread_barrierattr_destroy().
pthread_barrierattr_setpshared
Refer to pthread_barrierattr_getpshared().
pthread_barrier_destroy
The pthread_barrier_destroy() function shall destroy the barrier referenced by barrier and release any resources used by the barrier. The effect of subsequent...
pthread_barrier_wait
The pthread_barrier_wait() function shall synchronize participating threads at the barrier referenced by barrier. The calling thread shall block until the...
pthread_cancel
The pthread_cancel() function shall request that thread be canceled. The target thread's cancelability state and type determines when the cancellation takes...
pthread_cleanup_pop
The pthread_cleanup_pop() function shall remove the routine at the top of the calling thread's cancellation cleanup stack and optionally invoke it (if execute...
pthread_condattr_destroy
The pthread_condattr_destroy() function shall destroy a condition variable attributes object; the object becomes, in effect, uninitialized. An implementation...
pthread_condattr_getclock
The pthread_condattr_getclock() function shall obtain the value of the clock attribute from the attributes object referenced by attr. The...
pthread_condattr_getpshared
The pthread_condattr_getpshared() function shall obtain the value of the process-shared attribute from the attributes object referenced by attr. The...
pthread_condattr_init
Refer to pthread_condattr_destroy().
pthread_condattr_setclock
Refer to pthread_condattr_getclock().
pthread_condattr_setpshared
Refer to pthread_condattr_getpshared().
pthread_cond_broadcast
These functions shall unblock threads blocked on a condition variable. The pthread_cond_broadcast() function shall unblock all threads currently blocked on the...
pthread_cond_destroy
The pthread_cond_destroy() function shall destroy the given condition variable specified by cond; the object becomes, in effect, uninitialized. An...
pthread_cond_signal
Refer to pthread_cond_broadcast().
pthread_cond_timedwait
The pthread_cond_timedwait() and pthread_cond_wait() functions shall block on a condition variable. The application shall ensure that these functions are called...
pthread_create
The pthread_create() function shall create a new thread, with attributes specified by attr, within a process. If attr is NULL, the default attributes shall be...
pthread_detach
The pthread_detach() function shall indicate to the implementation that storage for the thread thread can be reclaimed when that thread terminates. If thread...
pthread_equal
This function shall compare the thread IDs t1 and t2.
pthread_exit
The pthread_exit() function shall terminate the calling thread and make the value value_ptr available to any successful join with the terminating thread. Any...
pthread_getconcurrency
Unbound threads in a process may or may not be required to be simultaneously active. By default, the threads implementation ensures that a sufficient number of...
pthread_getcpuclockid
The pthread_getcpuclockid() function shall return in clock_id the clock ID of the CPU-time clock of the thread specified by thread_id, if the thread specified...
pthread_getschedparam
The pthread_getschedparam() and pthread_setschedparam() functions shall, respectively, get and set the scheduling policy and parameters of individual threads...
pthread_getspecific
The pthread_getspecific() function shall return the value currently bound to the specified key on behalf of the calling thread. The pthread_setspecific()...
pthread_join
The pthread_join() function shall suspend execution of the calling thread until the target thread terminates, unless the target thread has already terminated...
pthread_key_create
The pthread_key_create() function shall create a thread-specific data key visible to all threads in the process. Key values provided by pthread_key_create() are...
pthread_key_delete
The pthread_key_delete() function shall delete a thread-specific data key previously returned by pthread_key_create(). The thread-specific data values...
pthread_kill
The pthread_kill() function shall request that a signal be delivered to the specified thread. As in kill(), if sig is zero, error checking shall be performed...
pthread_mutexattr_destroy
The pthread_mutexattr_destroy() function shall destroy a mutex attributes object; the object becomes, in effect, uninitialized. An implementation may cause...
pthread_mutexattr_getprioceiling
The pthread_mutexattr_getprioceiling() and pthread_mutexattr_setprioceiling() functions, respectively, shall get and set the priority ceiling attribute of a...
pthread_mutexattr_getprotocol
The pthread_mutexattr_getprotocol() and pthread_mutexattr_setprotocol() functions, respectively, shall get and set the protocol attribute of a mutex attributes...
pthread_mutexattr_getpshared
The pthread_mutexattr_getpshared() function shall obtain the value of the process-shared attribute from the attributes object referenced by attr. The...
pthread_mutexattr_getrobust
The pthread_mutexattr_getrobust() and pthread_mutexattr_setrobust() functions, respectively, shall get and set the mutex robust attribute. This attribute is set...
pthread_mutexattr_gettype
The pthread_mutexattr_gettype() and pthread_mutexattr_settype() functions, respectively, shall get and set the mutex type attribute. This attribute is set in...
pthread_mutexattr_init
Refer to pthread_mutexattr_destroy().
pthread_mutexattr_setprioceiling
Refer to pthread_mutexattr_getprioceiling().
pthread_mutexattr_setprotocol
Refer to pthread_mutexattr_getprotocol().
pthread_mutexattr_setpshared
Refer to pthread_mutexattr_getpshared().
pthread_mutexattr_setrobust
Refer to pthread_mutexattr_getrobust().
pthread_mutexattr_settype
Refer to pthread_mutexattr_gettype().
pthread_mutex_consistent
If mutex is a robust mutex in an inconsistent state, the pthread_mutex_consistent() function can be used to mark the state protected by the mutex referenced by...
pthread_mutex_destroy
The pthread_mutex_destroy() function shall destroy the mutex object referenced by mutex; the mutex object becomes, in effect, uninitialized. An implementation...
pthread_mutex_getprioceiling
The pthread_mutex_getprioceiling() function shall return the current priority ceiling of the mutex. The pthread_mutex_setprioceiling() function shall attempt to...
pthread_mutex_init
Refer to pthread_mutex_destroy().
pthread_mutex_lock
The mutex object referenced by mutex shall be locked by a call to pthread_mutex_lock() that returns zero or [EOWNERDEAD]. If the mutex is already locked by...
pthread_mutex_setprioceiling
Refer to pthread_mutex_getprioceiling().
pthread_mutex_timedlock
The pthread_mutex_timedlock() function shall lock the mutex object referenced by mutex. If the mutex is already locked, the calling thread shall block until the...
pthread_mutex_trylock
Refer to pthread_mutex_lock().
pthread_once
The first call to pthread_once() by any thread in a process, with a given once_control, shall call the init_routine with no arguments. Subsequent calls of...
pthread_rwlockattr_destroy
The pthread_rwlockattr_destroy() function shall destroy a read-write lock attributes object. A destroyed attr attributes object can be reinitialized using...
pthread_rwlockattr_getpshared
The pthread_rwlockattr_getpshared() function shall obtain the value of the process-shared attribute from the initialized attributes object referenced by attr...
pthread_rwlockattr_init
Refer to pthread_rwlockattr_destroy().
pthread_rwlockattr_setpshared
Refer to pthread_rwlockattr_getpshared().
pthread_rwlock_destroy
The pthread_rwlock_destroy() function shall destroy the read-write lock object referenced by rwlock and release any resources used by the lock. The effect of...
pthread_rwlock_rdlock
The pthread_rwlock_rdlock() function shall apply a read lock to the read-write lock referenced by rwlock. The calling thread acquires the read lock if a writer...
pthread_rwlock_timedrdlock
The pthread_rwlock_timedrdlock() function shall apply a read lock to the read-write lock referenced by rwlock as in the pthread_rwlock_rdlock() function...
pthread_rwlock_timedwrlock
The pthread_rwlock_timedwrlock() function shall apply a write lock to the read-write lock referenced by rwlock as in the pthread_rwlock_wrlock() function...
pthread_rwlock_tryrdlock
Refer to pthread_rwlock_rdlock().
pthread_rwlock_trywrlock
The pthread_rwlock_trywrlock() function shall apply a write lock like the pthread_rwlock_wrlock() function, with the exception that the function shall fail if...
pthread_rwlock_unlock
The pthread_rwlock_unlock() function shall release a lock held on the read-write lock object referenced by rwlock. Results are undefined if the read-write lock...
pthread_rwlock_wrlock
Refer to pthread_rwlock_trywrlock().
pthread_self
The pthread_self() function shall return the thread ID of the calling thread.
pthread_setcancelstate
The pthread_setcancelstate() function shall atomically both set the calling thread's cancelability state to the indicated state and return the previous...
pthread_setconcurrency
Refer to pthread_getconcurrency().
pthread_setschedparam
Refer to pthread_getschedparam().
pthread_setschedprio
The pthread_setschedprio() function shall set the scheduling priority for the thread whose thread ID is given by thread to the value given by prio. See...
pthread_setspecific
Refer to pthread_getspecific().
pthread_sigmask
The pthread_sigmask() function shall examine or change (or both) the calling thread's signal mask, regardless of the number of threads in the process. The...
pthread_spin_destroy
The pthread_spin_destroy() function shall destroy the spin lock referenced by lock and release any resources used by the lock. The effect of subsequent use of...
pthread_spin_lock
The pthread_spin_lock() function shall lock the spin lock referenced by lock. The calling thread shall acquire the lock if it is not held by another thread...
pthread_spin_unlock
The pthread_spin_unlock() function shall release the spin lock referenced by lock which was locked via the pthread_spin_lock() or pthread_spin_trylock()...
pthread_testcancel
Refer to pthread_setcancelstate().
ptsname
The ptsname() function shall return the name of the slave pseudo-terminal device associated with a master pseudo-terminal device. The fildes argument is a file...
putc
The putc() function shall be equivalent to fputc(), except that if it is implemented as a macro it may evaluate stream more than once, so the argument should...
putchar
The function call putchar(c) shall be equivalent to putc(c,stdout).
putchar_unlocked
Refer to getc_unlocked().
putc_unlocked
Refer to getc_unlocked().
putenv
The putenv() function shall use the string argument to set environment variable values. The string argument should point to a string of the form "name=value"...
putmsg
The putmsg() function shall create a message from a process buffer(s) and send the message to a STREAMS file. The message may contain either a data part, a...
puts
The puts() function shall write the string pointed to by s, followed by a <newline>, to the standard output stream stdout. The terminating null byte shall not...
pututxline
put an entry into the user accounting database
putwc
The putwc() function shall be equivalent to fputwc(), except that if it is implemented as a macro it may evaluate stream more than once, so the argument should...
putwchar
The function call putwchar(wc) shall be equivalent to putwc(wc,stdout).
pwrite
write on a file
qsort
The qsort() function shall sort an array of nel objects, the initial element of which is pointed to by base. The size of each object, in bytes, is specified by...
raise
The raise() function shall send the signal sig to the executing thread or process. If a signal handler is called, the raise() function shall not return until...
rand
For rand() and srand(): The rand() function shall compute a sequence of pseudo-random integers in the range [0,{RAND_MAX}] with a period of at least 232. The...
random
generate pseudo-random number
read
The read() function shall attempt to read nbyte bytes from the file associated with the open file descriptor, fildes, into the buffer pointed to by buf. The...
readdir
The type DIR, which is defined in the <dirent.h> header, represents a directory stream, which is an ordered sequence of all the directory entries in a...
readlink
The readlink() function shall place the contents of the symbolic link referred to by path in the buffer buf which has size bufsize. If the number of bytes in...
readv
The readv() function shall be equivalent to read(), except as described below. The readv() function shall place the input data into the iovcnt buffers specified...
realloc
The realloc() function shall deallocate the old object pointed to by ptr and return a pointer to a new object that has the size specified by size. The contents...
realpath
The realpath() function shall derive, from the pathname pointed to by file_name, an absolute pathname that resolves to the same directory entry, whose...
recv
The recv() function shall receive a message from a connection-mode or connectionless-mode socket. It is normally used with connected sockets because it does not...
recvfrom
The recvfrom() function shall receive a message from a connection-mode or connectionless-mode socket. It is normally used with connectionless-mode sockets...
recvmsg
The recvmsg() function shall receive a message from a connection-mode or connectionless-mode socket. It is normally used with connectionless-mode sockets...
regcomp
These functions interpret basic and extended regular expressions as described in the Base Definitions volume of POSIX.1‐2008, Chapter 9, Regular Expressions.
remainder
These functions shall return the floating-point remainder r=x-ny when y is non-zero. The value n is the integral value nearest the exact value x/y. When...
remove
The remove() function shall cause the file named by the pathname pointed to by path to be no longer accessible by that name. A subsequent attempt to open that...
remque
remove an element from a queue
remquo
The remquo(), remquof(), and remquol() functions shall compute the same remainder as the remainder(), remainderf(), and remainderl() functions, respectively. In...
rename
For rename(): The rename() function shall change the name of a file. The old argument points to the pathname of the file to be renamed. The new argument points...
rewind
reset the file position indicator in a stream
rewinddir
The rewinddir() function shall reset the position of the directory stream to which dirp refers to the beginning of the directory. It shall also cause the...
rint
These functions shall return the integral value (represented as a double) nearest x in the direction of the current rounding mode. The current rounding mode is...
rmdir
The rmdir() function shall remove a directory whose name is given by path. The directory shall be removed only if it is an empty directory. If the directory is...
round
These functions shall round their argument to the nearest integer value in floating-point format, rounding halfway cases away from zero, regardless of the...
scalbln
These functions shall compute x * FLT_RADIXn efficiently, not normally by computing FLT_RADIXn explicitly. An application wishing to check for error situations...
scandir
scan a directory
scanf
convert formatted input
sched_getparam
The sched_getparam() function shall return the scheduling parameters of a process specified by pid in the sched_param structure pointed to by param. If a...
sched_get_priority_max
The sched_get_priority_max() and sched_get_priority_min() functions shall return the appropriate maximum or minimum, respectively, for the scheduling policy...
sched_getscheduler
The sched_getscheduler() function shall return the scheduling policy of the process specified by pid. If the value of pid is negative, the behavior of the...
sched_rr_get_interval
The sched_rr_get_interval() function shall update the timespec structure referenced by the interval argument to contain the current execution time limit (that...
sched_setparam
The sched_setparam() function shall set the scheduling parameters of the process specified by pid to the values specified by the sched_param structure pointed...
sched_setscheduler
The sched_setscheduler() function shall set the scheduling policy and scheduling parameters of the process specified by pid to policy and the parameters...
sched_yield
The sched_yield() function shall force the running thread to relinquish the processor until it again becomes the head of its thread list. It takes no arguments.
seed48
seed a uniformly distributed pseudo-random non-negative long integer generator
seekdir
The seekdir() function shall set the position of the next readdir() operation on the directory stream specified by dirp to the position specified by loc. The...
select
synchronous I/O multiplexing
sem_close
The sem_close() function shall indicate that the calling process is finished using the named semaphore indicated by sem. The effects of calling sem_close() for...
semctl
The semctl() function operates on XSI semaphores (see the Base Definitions volume of POSIX.1‐2008, Section 4.16, Semaphore). It is unspecified whether this...
sem_destroy
The sem_destroy() function shall destroy the unnamed semaphore indicated by sem. Only a semaphore that was created using sem_init() may be destroyed using...
semget
The semget() function operates on XSI semaphores (see the Base Definitions volume of POSIX.1‐2008, Section 4.16, Semaphore). It is unspecified whether this...
sem_getvalue
The sem_getvalue() function shall update the location referenced by the sval argument to have the value of the semaphore referenced by sem without affecting the...
sem_init
The sem_init() function shall initialize the unnamed semaphore referred to by sem. The value of the initialized semaphore shall be value. Following a successful...
semop
The semop() function operates on XSI semaphores (see the Base Definitions volume of POSIX.1‐2008, Section 4.16, Semaphore). It is unspecified whether this...
sem_open
The sem_open() function shall establish a connection between a named semaphore and a process. Following a call to sem_open() with semaphore name name, the...
sem_post
The sem_post() function shall unlock the semaphore referenced by sem by performing a semaphore unlock operation on that semaphore. If the semaphore value...
sem_timedwait
The sem_timedwait() function shall lock the semaphore referenced by sem as in the sem_wait() function. However, if the semaphore cannot be locked without...
sem_trywait
The sem_trywait() function shall lock the semaphore referenced by sem only if the semaphore is currently not locked; that is, if the semaphore value is...
sem_unlink
The sem_unlink() function shall remove the semaphore named by the string name. If the semaphore named by name is currently referenced by other processes, then...
sem_wait
lock a semaphore
send
The send() function shall initiate transmission of a message from the specified socket to its peer. The send() function shall send a message only when the...
sendmsg
The sendmsg() function shall send a message through a connection-mode or connectionless-mode socket. If the socket is a connectionless-mode socket, the message...
sendto
The sendto() function shall send a message through a connection-mode or connectionless-mode socket. If the socket is a connectionless-mode socket, the message...
setbuf
assign buffering to a stream
setegid
If gid is equal to the real group ID or the saved set-group-ID, or if the process has appropriate privileges, setegid() shall set the effective group ID of the...
setenv
The setenv() function shall update or add a variable in the environment of the calling process. The envname argument points to a string containing the name of...
seteuid
If uid is equal to the real user ID or the saved set-user-ID, or if the process has appropriate privileges, seteuid() shall set the effective user ID of the...
setgid
If the process has appropriate privileges, setgid() shall set the real group ID, effective group ID, and the saved set-group-ID of the calling process to gid...
setgrent
reset the group database to the first entry
sethostent
network host database functions
setitimer
set the value of an interval timer
setjmp
A call to setjmp() shall save the calling environment in its env argument for later use by longjmp(). It is unspecified whether setjmp() is a macro or a...
setkey
The setkey() function provides access to an implementation-defined encoding algorithm. The argument of setkey() is an array of length 64 bytes containing only...
setlocale
The setlocale() function selects the appropriate piece of the global locale, as specified by the category and locale arguments, and can be used to change or...
setlogmask
set the log priority mask
setnetent
network database function
setpgid
The setpgid() function shall either join an existing process group or create a new process group within the session of the calling process. The process group ID...
setpgrp
If the calling process is not already a session leader, setpgrp() sets the process group ID of the calling process to the process ID of the calling process. If...
setpriority
set the nice value
setprotoent
network protocol database functions
setpwent
user database function
setregid
The setregid() function shall set the real and effective group IDs of the calling process. If rgid is -1, the real group ID shall not be changed; if egid is -1...
setreuid
The setreuid() function shall set the real and effective user IDs of the current process to the values specified by the ruid and euid arguments. If ruid or euid...
setrlimit
control maximum resource consumption
setservent
network services database functions
setsid
The setsid() function shall create a new session, if the calling process is not a process group leader. Upon return the calling process shall be the session...
setsockopt
The setsockopt() function shall set the option specified by the option_name argument, at the protocol level specified by the level argument, to the value...
setstate
switch pseudo-random number generator state arrays
setuid
If the process has appropriate privileges, setuid() shall set the real user ID, effective user ID, and the saved set-user-ID of the calling process to uid. If...
setutxent
reset the user accounting database to the first entry
setvbuf
The setvbuf() function may be used after the stream pointed to by stream is associated with an open file but before any other operation (other than an...
shmat
The shmat() function operates on XSI shared memory (see the Base Definitions volume of POSIX.1‐2008, Section 3.342, Shared Memory Object). It is unspecified...
shmctl
The shmctl() function operates on XSI shared memory (see the Base Definitions volume of POSIX.1‐2008, Section 3.342, Shared Memory Object). It is unspecified...
shmdt
The shmdt() function operates on XSI shared memory (see the Base Definitions volume of POSIX.1‐2008, Section 3.342, Shared Memory Object). It is unspecified...
shmget
The shmget() function operates on XSI shared memory (see the Base Definitions volume of POSIX.1‐2008, Section 3.342, Shared Memory Object). It is unspecified...
shm_open
The shm_open() function shall establish a connection between a shared memory object and a file descriptor. It shall create an open file description that refers...
shm_unlink
The shm_unlink() function shall remove the name of the shared memory object named by the string pointed to by name. If one or more references to the shared...
shutdown
The shutdown() function shall cause all or part of a full-duplex connection on the socket associated with the file descriptor socket to be shut down.
sigaction
The sigaction() function allows the calling process to examine and/or specify the action to be associated with a specific signal. The argument sig specifies the...
sigaddset
The sigaddset() function adds the individual signal specified by the signo to the signal set pointed to by set. Applications shall call either sigemptyset() or...
sigaltstack
The sigaltstack() function allows a process to define and examine the state of an alternate stack for signal handlers for the current thread. Signals that have...
sigdelset
The sigdelset() function deletes the individual signal specified by signo from the signal set pointed to by set. Applications should call either sigemptyset()...
sigemptyset
The sigemptyset() function initializes the signal set pointed to by set, such that all signals defined in POSIX.1‐2008 are excluded.
sigfillset
The sigfillset() function shall initialize the signal set pointed to by set, such that all signals defined in this volume of POSIX.1‐2008 are included.
sighold
Use of any of these functions is unspecified in a multi-threaded process. The sighold(), sigignore(), sigpause(), sigrelse(), and sigset() functions provide...
siginterrupt
The siginterrupt() function shall change the restart behavior when a function is interrupted by the specified signal.
sigismember
The sigismember() function shall test whether the signal specified by signo is a member of the set pointed to by set. Applications should call either...
siglongjmp
non-local goto with signal handling
signal
Use of this function is unspecified in a multi-threaded process. The signal() function chooses one of three ways in which receipt of the signal number sig is to...
signbit
The signbit() macro shall determine whether the sign of its argument value is negative. NaNs, zeros, and infinities have a sign bit.
signgam
log gamma function
sigpause
remove a signal from the signal mask and suspend the thread
sigpending
The sigpending() function shall store, in the location referenced by the set argument, the set of signals that are blocked from delivery to the calling thread...
sigprocmask
Refer to pthread_sigmask().
sigqueue
The sigqueue() function shall cause the signal specified by signo to be sent with the value specified by value to the process specified by pid. If signo is zero...
sigrelse
signal management
sigsetjmp
set jump point for a non-local goto
sigsuspend
The sigsuspend() function shall replace the current signal mask of the calling thread with the set of signals pointed to by sigmask and then suspend the thread...
sigtimedwait
The sigtimedwait() function shall be equivalent to sigwaitinfo() except that if none of the signals specified by set are pending, sigtimedwait() shall wait for...
sigwait
The sigwait() function shall select a pending signal from set, atomically clear it from the system's set of pending signals, and return that signal number in...
sigwaitinfo
wait for queued signals
sin
These functions shall compute the sine of their argument x, measured in radians. An application wishing to check for error situations should set errno to zero...
sinh
These functions shall compute the hyperbolic sine of their argument x. An application wishing to check for error situations should set errno to zero and call...
sinl
sine function
sleep
The sleep() function shall cause the calling thread to be suspended from execution until either the number of realtime seconds specified by the argument seconds...
snprintf
print formatted output
sockatmark
The sockatmark() function shall determine whether the socket specified by the descriptor s is at the out-of-band data mark (see Section 2.10.12, Socket...
socket
The socket() function shall create an unbound socket in a communications domain, and return a file descriptor that can be used in later function calls that...
socketpair
The socketpair() function shall create an unbound pair of connected sockets in a specified domain, of a specified type, under the protocol optionally specified...
sprintf
print formatted output
sqrt
These functions shall compute the square root of their argument x, x. An application wishing to check for error situations should set errno to zero and call...
srand
pseudo-random number generator
srand48
seed the uniformly distributed double-precision pseudo-random number generator
srandom
seed pseudo-random number generator
sscanf
convert formatted input
stat
get file status
statvfs
get file system information
stdin
A file with associated buffering is called a stream and is declared to be a pointer to a defined type FILE. The fopen() function shall create certain...
stpcpy
copy a string and return a pointer to the end of the result
stpncpy
copy fixed length string, returning a pointer to the array end
strcasecmp
The strcasecmp() and strcasecmp_l() functions shall compare, while ignoring differences in case, the string pointed to by s1 to the string pointed to by s2. The...
strcat
The strcat() function shall append a copy of the string pointed to by s2 (including the terminating NUL character) to the end of the string pointed to by s1...
strchr
The strchr() function shall locate the first occurrence of c (converted to a char) in the string pointed to by s. The terminating NUL character is considered to...
strcmp
The strcmp() function shall compare the string pointed to by s1 to the string pointed to by s2. The sign of a non-zero return value shall be determined by the...
strcoll
For strcoll(): The strcoll() and strcoll_l() functions shall compare the string pointed to by s1 to the string pointed to by s2, both interpreted as appropriate...
strcpy
For strcpy(): The stpcpy() and strcpy() functions shall copy the string pointed to by s2 (including the terminating NUL character) into the array pointed to by...
strcspn
The strcspn() function shall compute the length (in bytes) of the maximum initial segment of the string pointed to by s1 which consists entirely of bytes not...
strdup
The strdup() function shall return a pointer to a new string, which is a duplicate of the string pointed to by s. The returned pointer can be passed to free()...
strerror
For strerror(): The strerror() function shall map the error number in errnum to a locale-dependent error message string and shall return a pointer to it...
strfmon
The strfmon() function shall place characters into the array pointed to by s as controlled by the string pointed to by format. No more than maxsize bytes are...
strftime
For strftime(): The strftime() function shall place bytes into the array pointed to by s as controlled by the string pointed to by format. The format is a...
strlen
For strlen(): The strlen() function shall compute the number of bytes in the string to which s points, not including the terminating NUL character. The...
strncasecmp
case-insensitive string comparisons
strncat
The strncat() function shall append not more than n bytes (a NUL character and bytes that follow it are not appended) from the array pointed to by s2 to the end...
strncmp
The strncmp() function shall compare not more than n bytes (bytes that follow a NUL character are not compared) from the array pointed to by s1 to the array...
strncpy
For strncpy(): The stpncpy() and strncpy() functions shall copy not more than n bytes (bytes that follow a NUL character are not copied) from the array pointed...
strndup
duplicate a specific number of bytes from a string
strnlen
get length of fixed size string
strpbrk
The strpbrk() function shall locate the first occurrence in the string pointed to by s1 of any byte from the string pointed to by s2.
strptime
The strptime() function shall convert the character string pointed to by buf to values which are stored in the tm structure pointed to by tm, using the format...
strrchr
The strrchr() function shall locate the last occurrence of c (converted to a char) in the string pointed to by s. The terminating NUL character is considered to...
strsignal
The strsignal() function shall map the signal number in signum to an implementation-defined string and shall return a pointer to it. It shall use the same set...
strspn
The strspn() function shall compute the length (in bytes) of the maximum initial segment of the string pointed to by s1 which consists entirely of bytes from...
strstr
The strstr() function shall locate the first occurrence in the string pointed to by s1 of the sequence of bytes (excluding the terminating NUL character) in the...
strtod
These functions shall convert the initial portion of the string pointed to by nptr to double, float, and long double representation, respectively.
strtoimax
These functions shall be equivalent to the strtol(), strtoll(), strtoul(), and strtoull() functions, except that the initial portion of the string shall be...
strtok
For strtok(): A sequence of calls to strtok() breaks the string pointed to by s1 into a sequence of tokens, each of which is delimited by a byte from the string...
strtol
These functions shall convert the initial portion of the string pointed to by str to a type long and long long representation, respectively.
strtold
convert a string to a double-precision number
strtoll
convert a string to a long integer
strtoul
These functions shall convert the initial portion of the string pointed to by str to a type unsigned long and unsigned long long representation, respectively.
strtoumax
convert a string to an integer type
strxfrm
For strxfrm(): The strxfrm() and strxfrm_l() functions shall transform the string pointed to by s2 and place the resulting string into the array pointed to by...
swab
The swab() function shall copy nbytes bytes, which are pointed to by src, to the object pointed to by dest, exchanging adjacent bytes. The nbytes argument...
swprintf
print formatted wide-character output
swscanf
convert formatted wide-character input
symlink
The symlink() function shall create a symbolic link called path2 that contains the string pointed to by path1 (path2 is the name of the symbolic link created...
sync
The sync() function shall cause all information in memory that updates file systems to be scheduled for writing out to all file systems. The writing, although...
sysconf
The sysconf() function provides a method for the application to determine the current value of a configurable system limit or option (variable). The...
syslog
log a message
system
If command is a null pointer, the system() function shall determine whether the host environment has a command processor. If command is not a null pointer, the...
tan
These functions shall compute the tangent of their argument x, measured in radians. An application wishing to check for error situations should set errno to...
tanh
These functions shall compute the hyperbolic tangent of their argument x. An application wishing to check for error situations should set errno to zero and call...
tanl
tangent function
tcdrain
The tcdrain() function shall block until all output written to the object referred to by fildes is transmitted. The fildes argument is an open file descriptor...
tcflow
The tcflow() function shall suspend or restart transmission or reception of data on the object referred to by fildes, depending on the value of action. The...
tcflush
flush non-transmitted output data, non-read input data, or both
tcgetattr
The tcgetattr() function shall get the parameters associated with the terminal referred to by fildes and store them in the termios structure referenced by...
tcgetpgrp
The tcgetpgrp() function shall return the value of the process group ID of the foreground process group associated with the terminal. If there is no foreground...
tcgetsid
The tcgetsid() function shall obtain the process group ID of the session for which the terminal specified by fildes is the controlling terminal.
tcsendbreak
If the terminal is using asynchronous serial data transmission, tcsendbreak() shall cause transmission of a continuous stream of zero-valued bits for a specific...
tcsetattr
set the parameters associated with the terminal
tcsetpgrp
If the process has a controlling terminal, tcsetpgrp() shall set the foreground process group ID associated with the terminal to pgid_id. The application shall...
tdelete
The tdelete(), tfind(), tsearch(), and twalk() functions manipulate binary search trees. Comparisons are made with a user-supplied routine, the address of which...
telldir
The telldir() function shall obtain the current location associated with the directory stream specified by dirp. If the most recent operation on the directory...
tempnam
The tempnam() function shall generate a pathname that may be used for a temporary file. The tempnam() function allows the user to control the choice of a...
tfind
search binary search tree
tgamma
These functions shall compute the gamma function of x. An application wishing to check for error situations should set errno to zero and call...
time
The time() function shall return the value of time in seconds since the Epoch. The tloc argument points to an area where the return value is also stored. If...
timer_create
The timer_create() function shall create a per-process timer using the specified clock, clock_id, as the timing base. The timer_create() function shall return...
timer_delete
The timer_delete() function deletes the specified timer, timerid, previously created by the timer_create() function. If the timer is armed when timer_delete()...
timer_getoverrun
The timer_gettime() function shall store the amount of time until the specified timer, timerid, expires and the reload value of the timer into the space pointed...
times
The times() function shall fill the tms structure pointed to by buffer with time-accounting information. The tms structure is defined in <sys/times.h>. All...
timezone
difference from UTC and local standard time
tmpfile
The tmpfile() function shall create a temporary file and open a corresponding stream. The file shall be automatically deleted when all references to the file...
tmpnam
The tmpnam() function shall generate a string that is a valid pathname that does not name an existing file. The function is potentially capable of generating...
toascii
The toascii() function shall convert its argument into a 7-bit ASCII character.
tolower
For tolower(): The tolower() and tolower_l() functions have as a domain a type int, the value of which is representable as an unsigned char or the value of EOF...
_tolower
The _tolower() macro shall be equivalent to tolower(c) except that the application shall ensure that the argument c is an uppercase letter.
toupper
For toupper(): The toupper() and toupper_l() functions have as a domain a type int, the value of which is representable as an unsigned char or the value of EOF...
_toupper
The _toupper() macro shall be equivalent to toupper() except that the application shall ensure that the argument c is a lowercase letter.
towctrans
For towctrans(): The towctrans() and towctrans_l() functions shall transliterate the wide-character code wc using the mapping described by desc. The current...
towlower
For towlower(): The towlower() and towlower_l() functions have as a domain a type wint_t, the value of which the application shall ensure is a character...
towupper
For towupper(): The towupper() and towupper_l() functions have as a domain a type wint_t, the value of which the application shall ensure is a character...
trunc
These functions shall round their argument to the integer value, in floating format, nearest to but no larger in magnitude than the argument.
truncate
The truncate() function shall cause the regular file named by path to have a size which shall be equal to length bytes. If the file previously was larger than...
truncf
round to truncated integer value
tsearch
search a binary search tree
ttyname
The ttyname() function shall return a pointer to a string containing a null-terminated pathname of the terminal associated with file descriptor fildes. The...
twalk
traverse a binary search tree
tzset
The tzset() function shall use the value of the environment variable TZ to set time conversion information used by ctime(), localtime(), mktime(), and...
ulimit
The ulimit() function shall control process limits. The process limits that can be controlled by this function include the maximum size of a single file that...
umask
The umask() function shall set the file mode creation mask of the process to cmask and return the previous value of the mask. Only the file permission bits of...
uname
The uname() function shall store information identifying the current system in the structure pointed to by name. The uname() function uses the utsname structure...
ungetc
The ungetc() function shall push the byte specified by c (converted to an unsigned char) back onto the input stream pointed to by stream. The pushed-back bytes...
ungetwc
The ungetwc() function shall push the character corresponding to the wide-character code specified by wc back onto the input stream pointed to by stream. The...
unlink
The unlink() function shall remove a link to a file. If path names a symbolic link, unlink() shall remove the symbolic link named by path and shall not affect...
unlockpt
The unlockpt() function shall unlock the slave pseudo-terminal device associated with the master to which fildes refers. Conforming applications shall ensure...
unsetenv
The unsetenv() function shall remove an environment variable from the environment of the calling process. The name argument points to a string, which is the...
uselocale
The uselocale() function shall set the current locale for the current thread to the locale represented by newloc.
utime
The utime() function shall set the access and modification times of the file named by the path argument. If times is a null pointer, the access and modification...
utimensat
set file access and modification times relative to directory file descriptor
va_arg
Refer to the Base Definitions volume of POSIX.1‐2008, <stdarg.h>
vfprintf
The vdprintf(), vfprintf(), vprintf(), vsnprintf(), and vsprintf() functions shall be equivalent to the dprintf(), fprintf(), printf(), snprintf(), and...
vfscanf
The vscanf(), vfscanf(), and vsscanf() functions shall be equivalent to the scanf(), fscanf(), and sscanf() functions, respectively, except that instead of...
vfwprintf
The vfwprintf(), vswprintf(), and vwprintf() functions shall be equivalent to fwprintf(), swprintf(), and wprintf() respectively, except that instead of being...
vfwscanf
The vfwscanf(), vswscanf(), and vwscanf() functions shall be equivalent to the fwscanf(), swscanf(), and wscanf() functions, respectively, except that instead...
vprintf
format the output of a stdarg argument list
vscanf
format input of a stdarg argument list
vsnprintf
format output of a stdarg argument list
vsscanf
format input of a stdarg argument list
vswprintf
wide-character formatted output of a stdarg argument list
vswscanf
wide-character formatted input of a stdarg argument list
vwprintf
wide-character formatted output of a stdarg argument list
vwscanf
wide-character formatted input of a stdarg argument list
wait
The wait() and waitpid() functions shall obtain status information pertaining to one of the caller's child processes. Various options permit status information...
waitid
The waitid() function shall suspend the calling thread until one child of the process containing the calling thread changes state. It records the current state...
waitpid
wait for a child process to stop or terminate
wcpcpy
copy a wide-character string, returning a pointer to its end
wcpncpy
copy a fixed-size wide-character string, returning a pointer to its end
wcrtomb
convert a wide-character code to a character (restartable)
wcscasecmp
The wcscasecmp() and wcsncasecmp() functions are the wide-character equivalent of the strcasecmp() and strncasecmp() functions, respectively. The wcscasecmp()...
wcscat
The wcscat() function shall append a copy of the wide-character string pointed to by ws2 (including the terminating null wide-character code) to the end of the...
wcschr
The wcschr() function shall locate the first occurrence of wc in the wide-character string pointed to by ws. The application shall ensure that the value of wc...
wcscmp
The wcscmp() function shall compare the wide-character string pointed to by ws1 to the wide-character string pointed to by ws2. The sign of a non-zero return...
wcscoll
For wcscoll(): The wcscoll() and wcscoll_l() functions shall compare the wide-character string pointed to by ws1 to the wide-character string pointed to by ws2...
wcscpy
For wcscpy(): The wcpcpy() and wcscpy() functions shall copy the wide-character string pointed to by ws2 (including the terminating null wide-character code)...
wcscspn
The wcscspn() function shall compute the length (in wide characters) of the maximum initial segment of the wide-character string pointed to by ws1 which...
wcsdup
The wcsdup() function is the wide-character equivalent of the strdup() function. The wcsdup() function shall return a pointer to a new wide-character string...
wcsftime
convert date and time to a wide-character string
wcslen
For wcslen(): The wcslen() function shall compute the number of wide-character codes in the wide-character string to which ws points, not including the...
wcsncasecmp
case-insensitive wide-character string comparison
wcsncat
The wcsncat() function shall append not more than n wide-character codes (a null wide-character code and wide-character codes that follow it are not appended)...
wcsncmp
The wcsncmp() function shall compare not more than n wide-character codes (wide-character codes that follow a null wide-character code are not compared) from...
wcsncpy
For wcsncpy(): The wcpncpy() and wcsncpy() functions shall copy not more than n wide-character codes (wide-character codes that follow a null wide-character...
wcsnlen
get length of a fixed-sized wide-character string
wcsnrtombs
convert wide-character string to multi-byte string
wcspbrk
The wcspbrk() function shall locate the first occurrence in the wide-character string pointed to by ws1 of any wide-character code from the wide-character...
wcsrchr
The wcsrchr() function shall locate the last occurrence of wc in the wide-character string pointed to by ws. The application shall ensure that the value of wc...
wcsrtombs
For wcsrtombs(): The wcsrtombs() function shall convert a sequence of wide characters from the array indirectly pointed to by src into a sequence of...
wcsspn
The wcsspn() function shall compute the length (in wide characters) of the maximum initial segment of the wide-character string pointed to by ws1 which consists...
wcsstr
The wcsstr() function shall locate the first occurrence in the wide-character string pointed to by ws1 of the sequence of wide characters (excluding the...
wcstod
These functions shall convert the initial portion of the wide-character string pointed to by nptr to double, float, and long double representation...
wcstoimax
These functions shall be equivalent to the wcstol(), wcstoll(), wcstoul(), and wcstoull() functions, respectively, except that the initial portion of the wide...
wcstok
A sequence of calls to wcstok() shall break the wide-character string pointed to by ws1 into a sequence of tokens, each of which shall be delimited by a...
wcstol
These functions shall convert the initial portion of the wide-character string pointed to by nptr to long and long long, respectively.
wcstold
convert a wide-character string to a double-precision number
wcstoll
convert a wide-character string to a long integer
wcstombs
The wcstombs() function shall convert the sequence of wide-character codes that are in the array pointed to by pwcs into a sequence of characters that begins in...
wcstoul
The wcstoul() and wcstoull() functions shall convert the initial portion of the wide-character string pointed to by nptr to unsigned long and unsigned long long...
wcstoumax
convert a wide-character string to an integer type
wcswidth
The wcswidth() function shall determine the number of column positions required for n wide-character codes (or fewer than n wide-character codes if a null...
wcsxfrm
For wcsxfrm(): The wcsxfrm() and wcsxfrm_l() functions shall transform the wide-character string pointed to by ws2 and place the resulting wide-character string...
wctob
The wctob() function shall determine whether c corresponds to a member of the extended character set whose character representation is a single byte when in the...
wctomb
The wctomb() function shall determine the number of bytes needed to represent the character corresponding to the wide-character code whose value is wchar...
wctrans
For wctrans(): The wctrans() and wctrans_l() functions are defined for valid character mapping names identified in the current locale. The charclass is a string...
wctype
For wctype(): The wctype() and wctype_l() functions are defined for valid character class names as defined in the current locale or in the locale represented by...
wcwidth
The wcwidth() function shall determine the number of column positions required for the wide character wc. The application shall ensure that the value of wc is a...
wmemchr
The wmemchr() function shall locate the first occurrence of wc in the initial n wide characters of the object pointed to by ws. This function shall not be...
wmemcmp
The wmemcmp() function shall compare the first n wide characters of the object pointed to by ws1 to the first n wide characters of the object pointed to by ws2...
wmemcpy
The wmemcpy() function shall copy n wide characters from the object pointed to by ws2 to the object pointed to by ws1. This function shall not be affected by...
wmemmove
The wmemmove() function shall copy n wide characters from the object pointed to by ws2 to the object pointed to by ws1. Copying shall take place as if the n...
wmemset
The wmemset() function shall copy the value of wc into each of the first n wide characters of the object pointed to by ws. This function shall not be affected...
wordexp
The wordexp() function shall perform word expansions as described in the Shell and Utilities volume of POSIX.1‐2008, Section 2.6, Word Expansions, subject to...
wprintf
print formatted wide-character output
write
The write() function shall attempt to write nbyte bytes from the buffer pointed to by buf to the file associated with the open file descriptor, fildes. Before...
writev
The writev() function shall be equivalent to write(), except as described below. The writev() function shall gather output data from the iovcnt buffers...
wscanf
convert formatted wide-character input
y0
The y0(), y1(), and yn() functions shall compute Bessel functions of x of the second kind of orders 0, 1, and n, respectively. An application wishing to check...
Special Files (Section 4)
cciss
cciss is a block driver for older HP Smart Array RAID controllers.Options cciss_allow_hpsa=1: This option prevents the cciss driver from attempting to drive any...
console_codes
The Linux console implements a large subset of the VT102 and ECMA-48/ISO 6429/ANSI X3.64 terminal controls, plus certain private-mode sequences for changing the...
console_ioctl
The following Linux-specific ioctl(2) requests are supported. Each requires a third argument, assumed here to be argp.
cpuid
CPUID provides an interface for querying information about the x86 CPU. This device is accessed by lseek(2) or pread(2) to the appropriate CPUID level and...
dsp56k
The Motorola DSP56001 is a fully programmable 24-bit digital signal processor found in Atari Falcon030-compatible computers. The dsp56k special file is used to...
fd
fd special files access the floppy disk drives in raw mode.
full
File /dev/full has major device number 1 and minor device number 7. Writes to the /dev/full device will fail with an ENOSPC error. This can be used to test how...
hd
The hd* devices are block devices to access MFM/IDE hard disk drives in raw mode. The master drive on the primary IDE controller (major device number 3) is hda...
hpsa
hpsa is a SCSI driver for HP Smart Array RAID controllers.Options hpsa_allow_any=1: This option allows the driver to attempt to operate on any HP Smart Array...
initrd
The special file /dev/initrd is a read-only block device. This device is a RAM disk that is initialized (e.g., loaded) by the boot loader before the kernel is...
intro
Section 4 of the manual describes special files (devices).
lirc
The /dev/lirc* character devices provide a low-level bi-directional interface to infra-red (IR) remotes. When receiving data, the driver works in two different...
loop
The loop device is a block device that maps its data blocks not to a physical device such as a hard disk or optical disk drive, but to the blocks of a regular...
lp
line printer devices
mem
/dev/mem is a character device file that is an image of the main memory of the computer. It may be used, for example, to examine (and even patch) the system...
mouse
Introduction The pinout of the usual 9 pin plug as used for serial mice is:Microsoft protocol The Microsoft protocol uses 1 start bit, 7 data bits, no parity...
msr
/dev/cpu/CPUNUM/msr provides an interface to read and write the model-specific registers (MSRs) of an x86 CPU. CPUNUM is the number of the CPU to access as...
null
Data written to the /dev/null and /dev/zero special files is discarded. Reads from /dev/null always return end of file (i.e., read(2) returns 0), whereas reads...
pts
The file /dev/ptmx is a character file with major number 5 and minor number 2, usually of mode 0666 and owner.group of root.root. It is used to create a...
ram
The ram device is a block device to access the ram disk in raw mode.
random
The character special files /dev/random and /dev/urandom (present since Linux 1.3.30) provide an interface to the kernel's random number generator. File...
rtc
This is the interface to drivers for real-time clocks (RTCs). Most computers have one or more hardware clocks which record the current "wall clock" time. These...
sd
driver for SCSI disk drives
sk98lin
Note: This obsolete driver was removed from the kernel in version 2.6.26. sk98lin is the Gigabit Ethernet driver for Marvell and SysKonnect network adapter...
st
The st driver provides the interface to a variety of SCSI tape devices. Currently, the driver takes control of all detected devices of type “sequential-access”...
tty
The file /dev/tty is a character file with major number 5 and minor number 0, usually of mode 0666 and owner.group root.tty. It is a synonym for the controlling...
tty_ioctl
The ioctl(2) call for terminals and serial ports accepts many possible command arguments. Most require a third argument, of varying type, here called argp or...
ttyS
ttyS[0-3] are character devices for the serial terminal lines.
vcs
/dev/vcs0 is a character device with major number 7 and minor number 0, usually of mode 0644 and owner root.tty. It refers to the memory of the currently...
wavelan
This driver is obsolete: it was removed from the kernel in version 2.6.35. wavelan is the low-level device driver for the NCR / AT&T / Lucent WaveLAN ISA and...
File Formats (Section 5)
acct
If the kernel is built with the process accounting option enabled (CONFIG_BSD_PROCESS_ACCT), then calling acct(2) starts process accounting, for example...
charmap
A character set description (charmap) defines all available characters and their encodings in a character set.
core
The default action of certain signals is to cause a process to terminate and produce a core dump file, a disk file containing an image of the process's memory...
dir_colors
The program ls(1) uses the environment variable LS_COLORS to determine the colors in which the filenames are to be displayed. This environment variable is...
elf
The header file <elf.h> defines the format of ELF executable binary files. Amongst these files are normal executable files, relocatable object files, core...
filesystems
When, as is customary, the proc filesystem is mounted on /proc, you can find in the file /proc/filesystems which filesystems your kernel currently supports; see...
ftpusers
The text file ftpusers contains a list of users that may not log in using the File Transfer Protocol (FTP) server daemon. This file is used not merely for...
gai.conf
A call to getaddrinfo(3) might return multiple answers. According to RFC 3484 these answers must be sorted so that the answer with the highest success rate is...
group
The /etc/group file is a text file that defines the groups on the system.
host.conf
The file /etc/host.conf contains configuration information specific to the resolver library. It should contain one configuration keyword per line, followed by...
hosts
This manual page describes the format of the /etc/hosts file. This file is a simple text file that associates IP addresses with hostnames, one line per IP...
hosts.equiv
The file /etc/hosts.equiv allows or denies hosts and users to use the r-commands (e.g., rlogin, rsh, or rcp) without supplying a password. The file uses the...
intro
Section 5 of the manual describes various file formats, as well as the corresponding C structures, if any.
issue
The file /etc/issue is a text file which contains a message or system identification to be printed before the login prompt. It may contain various @char and...
locale
The locale definition file contains all the information that the localedef(1) command needs to convert it into the binary locale database. The definition files...
motd
The contents of /etc/motd are displayed by login(1) after a successful login but just before it executes the login shell. The abbreviation "motd" stands for...
networks
The file /etc/networks is a plain ASCII file that describes known DARPA networks and symbolic names for these networks.
nologin
If the file /etc/nologin exists and is readable, login(1) will allow access only to root. Other users will be shown the contents of this file and their logins...
nscd.conf
The file /etc/nscd.conf is read from nscd(8) at startup. Each line specifies either an attribute and a value, or an attribute, service, and a value. Fields are...
nss
Each call to a function which retrieves data from a system database like the password or group database is handled by the Name Service Switch implementation in...
nsswitch.conf
The Name Service Switch (NSS) configuration file, /etc/nsswitch.conf, is used by the GNU C Library to determine the sources from which to obtain name-service...
passwd
The /etc/passwd file is a text file that describes user login accounts for the system. It should have read permission allowed for all users (many utilities...
proc
The proc filesystem is a pseudo-filesystem which provides an interface to kernel data structures. It is commonly mounted at /proc. Most of it is read-only, but...
protocols
This file is a plain ASCII file, describing the various DARPA internet protocols that are available from the TCP/IP subsystem. It should be consulted instead of...
repertoiremap
A repertoire map defines mappings between symbolic character names (mnemonics) and Unicode code points when compiling a locale with localedef(1).
resolv.conf
The resolver is a set of routines in the C library that provide access to the Internet Domain Name System (DNS). The resolver configuration file contains...
rpc
The rpc file contains user readable names that can be used in place of RPC program numbers. Each line has the following information: name of server for the RPC...
securetty
The file /etc/securetty contains the names of terminals (one per line, without leading /dev/) which are considered secure for the transmission of certain...
services
services is a plain ASCII file providing a mapping between human-friendly textual names for internet services, and their underlying assigned port numbers and...
shells
/etc/shells is a text file which contains the full pathnames of valid login shells. This file is consulted by chsh(1) and available to be queried by other...
slabinfo
Frequently used objects in the Linux kernel (buffer heads, inodes, dentries, etc.) have their own cache. The file /proc/slabinfo gives statistics.
termcap
The termcap database is an obsolete facility for describing the capabilities of character-cell terminals and printers. It is retained only for capability with...
ttytype
The /etc/ttytype file associates termcap(5)/terminfo(5) terminal type names with tty lines. Each line consists of a terminal type, followed by whitespace...
tzfile
This page describes the structure of the timezone files used by tzset(3). These files are typically found under one of the directories /usr/lib/zoneinfo or...
utmp
The utmp file allows one to discover information about who is currently using the system. There may be more users currently using the system, because not all...
Games (Section 6)
intro
Section 6 of the manual describes all the games and funny little programs available on the system.
Miscellanea (Section 7)
aio
The POSIX asynchronous I/O (AIO) interface allows applications to initiate one or more I/O operations that are performed asynchronously (i.e., in the...
armscii-8
The Armenian Standard Code for Information Interchange, 8-bit coded character set.ArmSCII-8 characters The following table displays the characters in ArmSCII-8...
arp
This kernel protocol module implements the Address Resolution Protocol defined in RFC 826. It is used to convert between Layer2 hardware addresses and IPv4...
ascii
ASCII is the American Standard Code for Information Interchange. It is a 7-bit code. Many 8-bit codes (e.g., ISO 8859-1) contain ASCII as their lower half. The...
attributes
Note: the text of this man page is based on the material taken from the "POSIX Safety Concepts" section of the GNU C Library manual. Further details on the...
bootparam
The Linux kernel accepts certain 'command-line options' or 'boot time parameters' at the moment it is started. In general this is used to supply the kernel with...
capabilities
For the purpose of performing permission checks, traditional UNIX implementations distinguish two categories of processes: privileged processes (whose effective...
cgroup_namespaces
For an overview of namespaces, see namespaces(7). Cgroup namespaces virtualize the view of a process's cgroups (see cgroups(7)) as seen via /proc/[pid]/cgroup...
cgroups
Control cgroups, usually referred to as cgroups, are a Linux kernel feature which which allow processes to be organized into hierarchical groups whose usage of...
charsets
This manual page gives an overview on different character set standards and how they were used on Linux before Unicode became ubiquitous. Some of this...
complex
Complex numbers are numbers of the form z = a+b*i, where a and b are real numbers and i = sqrt(-1), so that i*i = -1. There are other ways to represent that...
cp1251
The Windows Code Pages include several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). CP 1251 encodes the characters used in Cyrillic...
cp1252
The Windows Code Pages include several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). CP 1252 encodes the characters used in many West...
cpuset
The cpuset filesystem is a pseudo-filesystem interface to the kernel cpuset mechanism, which is used to control the processor placement and memory placement of...
credentials
Process ID (PID) Each process has a unique nonnegative integer identifier that is assigned when the process is created using fork(2). A process can obtain its...
ddp
Linux implements the AppleTalk protocols described in Inside AppleTalk. Only the DDP layer and AARP are present in the kernel. They are designed to be used via...
environ
The variable environ points to an array of pointers to strings called the "environment". The last pointer in this array has the value NULL. (This variable must...
epoll
The epoll API performs a similar task to poll(2): monitoring multiple file descriptors to see if I/O is possible on any of them. The epoll API can be used...
fanotify
The fanotify API provides notification and interception of filesystem events. Use cases include virus scanning and hierarchical storage management. Currently...
feature_test_macros
Feature test macros allow the programmer to control the definitions that are exposed by system header files when a program is compiled. NOTE: In order to be...
fifo
A FIFO special file (a named pipe) is similar to a pipe, except that it is accessed as part of the filesystem. It can be opened by multiple processes for...
futex
The Linux kernel provides futexes ("Fast user-space mutexes") as a building block for fast user-space locking and semaphores. Futexes are very basic and lend...
glob
Long ago, in UNIX V6, there was a program /etc/glob that would expand wildcard patterns. Soon afterward this became a shell built-in. These days there is also a...
hier
description of the filesystem hierarchy
hostname
Hostnames are domains, where a domain is a hierarchical, dot-separated list of subdomains; for example, the machine monet, in the Berkeley subdomain of the EDU...
icmp
This kernel protocol module implements the Internet Control Message Protocol defined in RFC 792. It is used to signal error conditions and for diagnosis. The...
inotify
The inotify API provides a mechanism for monitoring filesystem events. Inotify can be used to monitor individual files, or to monitor directories. When a...
intro
Section 7 of the manual provides overviews on various topics, and describes conventions and protocols, character set standards, the standard filesystem layout...
ip
Linux implements the Internet Protocol, version 4, described in RFC 791 and RFC 1122. ip contains a level 2 multicasting implementation conforming to RFC 1112...
ipv6
Linux 2.2 optionally implements the Internet Protocol, version 6. This man page contains a description of the IPv6 basic API as implemented by the Linux kernel...
iso_8859-1
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-1 encodes the characters used in many...
iso_8859-10
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-10 encodes the characters used in...
iso_8859-11
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-11 encodes the characters used in the...
iso_8859-13
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-13 encodes the characters used in...
iso_8859-14
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-14 encodes the characters used in...
iso_8859-15
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-15 encodes the characters used in many...
iso_8859-16
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-16 encodes the Latin characters used in...
iso_8859-2
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-2 encodes the Latin characters used in...
iso_8859-3
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-3 encodes the characters used in...
iso_8859-4
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-4 encodes the characters used in...
iso_8859-5
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-5 encodes the Cyrillic characters used...
iso_8859-6
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-6 encodes the characters used in the...
iso_8859-7
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-7 encodes the characters used in modern...
iso_8859-8
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-8 encodes the characters used in Modern...
iso_8859-9
The ISO 8859 standard includes several 8-bit extensions to the ASCII character set (also known as ISO 646-IRV). ISO 8859-9 encodes the characters used in...
koi8-r
RFC 1489 defines an 8-bit character set, KOI8-R. KOI8-R encodes the characters used in Russian.KOI8-R characters The following table displays the characters in...
koi8-u
RFC 2310 defines an 8-bit character set, KOI8-U. KOI8-U encodes the characters used in Ukrainian and Byelorussian.KOI8-U characters The following table displays...
libc
The term "libc" is commonly used as a shorthand for the "standard C library", a library of standard functions that can be used by all C programs (and sometimes...
locale
A locale is a set of language and cultural rules. These cover aspects such as language for messages, different character sets, lexicographic conventions, and so...
mailaddr
This manual page gives a brief introduction to SMTP mail addresses, as used on the Internet. These addresses are in the general format user@domain where a...
man
This manual page explains the groff an.tmac macro package (often called the man macro package). This macro package should be used by developers when writing or...
man-pages
This page describes the conventions that should be employed when writing man pages for the Linux man-pages project, which documents the user-space API provided...
math_error
When an error occurs, most library functions indicate this fact by returning a special value (e.g., -1 or NULL). Because they typically return a floating-point...
mdoc
The -mdoc package is a set of content-based and domain-based macros used to format the BSD man pages. The macro names and their meanings are listed below for...
mdoc.samples
A tutorial sampler for writing BSD manual pages with the -mdoc macro package, a content-based and domain-based formatting package for troff(1). Its predecessor...
mount_namespaces
For an overview of namespaces, see namespaces(7). Mount namespaces provide isolation of the list of mount points seen by the processes in each namespace...
mq_overview
POSIX message queues allow processes to exchange data in the form of messages. This API is distinct from that provided by System V message queues (msgget(2)...
namespaces
A namespace wraps a global system resource in an abstraction that makes it appear to the processes within the namespace that they have their own isolated...
netdevice
This man page describes the sockets interface which is used to configure network devices. Linux supports some standard ioctls to configure network devices. They...
netlink
Netlink is used to transfer information between the kernel and user-space processes. It consists of a standard sockets-based interface for user space processes...
nptl
NPTL (Native POSIX Threads Library) is the GNU C library POSIX threads implementation that is used on modern Linux systems.NPTL and signals NPTL makes internal...
numa
Non-Uniform Memory Access (NUMA) refers to multiprocessor systems whose memory is divided into multiple memory nodes. The access time of a memory node depends...
operator
This manual page lists C operators and their precedence in evaluation.
packet
Packet sockets are used to receive or send raw packets at the device driver (OSI Layer 2) level. They allow the user to implement protocol modules in user space...
path_resolution
Some UNIX/Linux system calls have as parameter one or more filenames. A filename (or pathname) is resolved as follows.Step 1: start of the resolution process If...
pid_namespaces
For an overview of namespaces, see namespaces(7). PID namespaces isolate the process ID number space, meaning that processes in different PID namespaces can...
pipe
Pipes and FIFOs (also known as named pipes) provide a unidirectional interprocess communication channel. A pipe has a read end and a write end. Data written to...
posixoptions
The POSIX standard (the information below is from POSIX.1-2001) describes a set of behaviors and interfaces for a compliant system. However, many interfaces are...
pthreads
POSIX.1 specifies a set of interfaces (functions, header files) for threaded programming commonly known as POSIX threads, or Pthreads. A single process can...
pty
A pseudoterminal (sometimes abbreviated "pty") is a pair of virtual character devices that provide a bidirectional communication channel. One end of the channel...
raw
Raw sockets allow new IPv4 protocols to be implemented in user space. A raw socket receives or sends the raw datagram not including link level headers. The IPv4...
regex
Regular expressions ("RE"s), as defined in POSIX.2, come in two forms: modern REs (roughly those of egrep; POSIX.2 calls these "extended" REs) and obsolete REs...
rtld-audit
The GNU dynamic linker (run-time linker) provides an auditing API that allows an application to be notified when various dynamic linking events occur. This API...
rtnetlink
Rtnetlink allows the kernel's routing tables to be read and altered. It is used within the kernel to communicate between various subsystems, though this usage...
sched
API summary The Linux scheduling APIs are as follows:Scheduling policies The scheduler is the kernel component that decides which runnable thread will be...
sem_overview
POSIX semaphores allow processes and threads to synchronize their actions. A semaphore is an integer whose value is never allowed to fall below zero. Two...
shm_overview
The POSIX shared memory API allows processes to communicate information by sharing a region of memory.
sigevent
The sigevent structure is used by various APIs to describe the way a process is to be notified about an event (e.g., completion of an asynchronous request...
signal
Linux supports both POSIX reliable signals (hereinafter "standard signals") and POSIX real-time signals.Signal dispositions Each signal has a current...
socket
This manual page describes the Linux networking socket layer user interface. The BSD compatible sockets are the uniform interface between the user process and...
spufs
The SPU filesystem is used on PowerPC machines that implement the Cell Broadband Engine Architecture in order to access Synergistic Processor Units (SPUs). The...
standards
The CONFORMING TO section that appears in many manual pages identifies various standards to which the documented interface conforms. The following list briefly...
suffixes
It is customary to indicate the contents of a file with the file suffix, which consists of a period, followed by one or more letters. Many standard utilities...
svipc
This manual page refers to the Linux implementation of the System V interprocess communication (IPC) mechanisms: message queues, semaphore sets, and shared...
symlink
Symbolic links are files that act as pointers to other files. To understand their behavior, you must first understand how hard links work. A hard link to a file...
tcp
This is an implementation of the TCP protocol defined in RFC 793, RFC 1122 and RFC 2001 with the NewReno and SACK extensions. It provides a reliable...
termio
termio is the name of the old System V terminal driver interface. This interface defined a termio structure used to store terminal settings, and a range of...
time
Real time and process time Real time is defined as time measured from some fixed point, either from a standard point in the past (see the description of the...
udp
This is an implementation of the User Datagram Protocol described in RFC 768. It implements a connectionless, unreliable datagram packet service. Packets may be...
udplite
This is an implementation of the Lightweight User Datagram Protocol (UDP-Lite), as described in RFC 3828. UDP-Lite is an extension of UDP (RFC 768) to support...
unicode
The international standard ISO 10646 defines the Universal Character Set (UCS). UCS contains all characters of all other character set standards. It also...
units
Decimal prefixes The SI system of units uses prefixes that indicate powers of ten. A kilometer is 1000 meter, and a megawatt is 1000000 watt. Below the standard...
unix
The AF_UNIX (also known as AF_LOCAL) socket family is used to communicate between processes on the same machine efficiently. Traditionally, UNIX domain sockets...
uri
A Uniform Resource Identifier (URI) is a short string of characters identifying an abstract or physical resource (for example, a web page). A Uniform Resource...
user_namespaces
For an overview of namespaces, see namespaces(7). User namespaces isolate security-related identifiers and attributes, in particular, user IDs and group IDs...
utf-8
The Unicode 3.0 character set occupies a 16-bit code space. The most obvious Unicode encoding (known as UCS-2) consists of a sequence of 16-bit words. Such...
vdso
The "vDSO" (virtual dynamic shared object) is a small shared library that the kernel automatically maps into the address space of all user-space applications...
x25
X25 sockets provide an interface to the X.25 packet layer protocol. This allows applications to communicate over a public X.25 data network as standardized by...
xattr
Extended attributes are name:value pairs associated permanently with files and directories, similar to the environment strings associated with a process. An...
System Administration (Section 8)
cons.saver
Invoke this helper program with the Ctrl-o key combination to save and restore the user session on the screen.
iconvconfig
The iconv(3) function internally uses gconv modules to convert to and from a character set. A configuration file is used to determine the needed modules for a...
intro
Section 8 of the manual describes commands which either can be or are used only by the superuser, like system-administration commands, daemons, and...
ldconfig
ldconfig creates the necessary links and cache to the most recent shared libraries found in the directories specified on the command line, in the file...
ld.so
The programs ld.so and ld-linux.so* find and load the shared objects (shared libraries) needed by a program, prepare the program to run, and then run it. Linux...
nscd
Nscd is a daemon that provides a cache for the most common name service requests. The default configuration file, /etc/nscd.conf, determines the behavior of the...
sln
The sln program creates symbolic links. Unlike the ln(1) program, it is statically linked. This means that if for some reason the dynamic linker is not working...
tzselect
The tzselect program asks the user for information about the current location, and outputs the resulting timezone description to standard output. The output is...
zdump
Zdump prints the current time in each zonename named on the command line.
zic
Zic reads text from the file(s) named on the command line and creates the time conversion information files specified in this input. If a filename is -, the...