unlocked_stdio man page

getc_unlocked, getchar_unlocked, putc_unlocked, putchar_unlocked — nonlocking stdio functions


#include <stdio.h>

int getc_unlocked(FILE *stream);
int getchar_unlocked(void);
int putc_unlocked(int c, FILE *stream);
int putchar_unlocked(int c);

void clearerr_unlocked(FILE *stream);
int feof_unlocked(FILE *stream);
int ferror_unlocked(FILE *stream);
int fileno_unlocked(FILE *stream);
int fflush_unlocked(FILE *stream);
int fgetc_unlocked(FILE *stream);
int fputc_unlocked(int c, FILE *stream);
size_t fread_unlocked(void *ptr, size_t size, size_t n,
                      FILE *stream);
size_t fwrite_unlocked(const void *ptr, size_t size, size_t n,
                      FILE *stream);

char *fgets_unlocked(char *s, int n, FILE *stream);
int fputs_unlocked(const char *s, FILE *stream);

#include <wchar.h>

wint_t getwc_unlocked(FILE *stream);
wint_t getwchar_unlocked(void);
wint_t fgetwc_unlocked(FILE *stream);
wint_t fputwc_unlocked(wchar_t wc, FILE *stream);
wint_t putwc_unlocked(wchar_t wc, FILE *stream);
wint_t putwchar_unlocked(wchar_t wc);
wchar_t *fgetws_unlocked(wchar_t *ws, int n, FILE *stream);
int fputws_unlocked(const wchar_t *ws, FILE *stream);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

getc_unlocked(), getchar_unlocked(), putc_unlocked(), putchar_unlocked():

/* Since glibc 2.24: */ _POSIX_C_SOURCE >= 199309L
   || /* Glibc versions <= 2.23: */ _POSIX_C_SOURCE
   || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE

clearerr_unlocked(), feof_unlocked(), ferror_unlocked(), fileno_unlocked(), fflush_unlocked(), fgetc_unlocked(), fputc_unlocked(), fread_unlocked(), fwrite_unlocked():

/* Glibc since 2.19: */ _DEFAULT_SOURCE
   || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE

fgets_unlocked(), fputs_unlocked(), getwc_unlocked(), getwchar_unlocked(), fgetwc_unlocked(), fputwc_unlocked(), putwchar_unlocked(), fgetws_unlocked(), fputws_unlocked():



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 themselves, and do not test for the presence of locks set by others) and hence are thread-unsafe. See flockfile(3).


For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
getc_unlocked(), putc_unlocked(), clearerr_unlocked(), fflush_unlocked(), fgetc_unlocked(), fputc_unlocked(), fread_unlocked(), fwrite_unlocked(), fgets_unlocked(), fputs_unlocked(), getwc_unlocked(), fgetwc_unlocked(), fputwc_unlocked(), putwc_unlocked(), fgetws_unlocked(), fputws_unlocked() Thread safety MT-Safe race:stream
getchar_unlocked(), getwchar_unlocked() Thread safety MT-Unsafe race:stdin
putchar_unlocked(), putwchar_unlocked() Thread safety MT-Unsafe race:stdout
feof_unlocked(), ferror_unlocked(), fileno_unlocked() Thread safety MT-Safe

Conforming to

The four functions getc_unlocked(), getchar_unlocked(), putc_unlocked(), putchar_unlocked() are in POSIX.1-2001 and POSIX.1-2008.

The nonstandard *_unlocked() variants occur on a few UNIX systems, and are available in recent glibc. They should probably not be used.

See Also

flockfile(3), stdio(3)


This page is part of release 4.16 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Referenced By

ferror(3), fflush(3), fgetc(3), fgetwc(3), fgetws(3), flockfile(3), fputwc(3), fputws(3), fread(3), gets(3), getwchar(3), puts(3), putwchar(3), stdio(3).

The man pages clearerr_unlocked(3), feof_unlocked(3), ferror_unlocked(3), fflush_unlocked(3), fgetc_unlocked(3), fgets_unlocked(3), fgetwc_unlocked(3), fgetws_unlocked(3), fileno_unlocked(3), fputc_unlocked(3), fputs_unlocked(3), fputwc_unlocked(3), fputws_unlocked(3), fread_unlocked(3), fwrite_unlocked(3), getchar_unlocked(3), getc_unlocked(3), getwchar_unlocked(3), getwc_unlocked(3), putchar_unlocked(3), putc_unlocked(3), putwchar_unlocked(3) and putwc_unlocked(3) are aliases of unlocked_stdio(3).

2017-09-15 Linux Programmer's Manual