sys_select.h - Man Page

select types


This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


#include <sys/select.h>


The <sys/select.h> header shall define the timeval structure, which shall include at least the following members:

time_t         tv_sec      Seconds.
suseconds_t    tv_usec     Microseconds.

The <sys/select.h> header shall define the time_t and suseconds_t types as described in <sys/types.h>.

The <sys/select.h> header shall define the sigset_t type as described in <signal.h>.

The <sys/select.h> header shall define the timespec structure as described in <time.h>.

The <sys/select.h> header shall define the fd_set type as a structure.

The <sys/select.h> header shall define the following symbolic constant, which shall have a value suitable for use in #if preprocessing directives:


Maximum number of file descriptors in an fd_set structure.

The following shall be declared as functions, defined as macros, or both. If functions are declared, function prototypes shall be provided.

void FD_CLR(int, fd_set *);
int  FD_ISSET(int, fd_set *);
void FD_SET(int, fd_set *);
void FD_ZERO(fd_set *);

If implemented as macros, these may evaluate their arguments more than once, so applications should ensure that the arguments they supply are never expressions with side-effects.

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

int  pselect(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
         const struct timespec *restrict, const sigset_t *restrict);
int  select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
         struct timeval *restrict);

Inclusion of the <sys/select.h> header may make visible all symbols from the headers <signal.h> and <time.h>.

The following sections are informative.

Application Usage




Future Directions


See Also

<signal.h>, <sys_time.h>, <sys_types.h>, <time.h>

The System Interfaces volume of POSIX.1-2017, pselect()

Referenced By

pselect(3p), sys_time.h(0p).

2017 IEEE/The Open Group POSIX Programmer's Manual