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UNLOCKED_STDIO(3) Linux Programmer's Manual UNLOCKED_STDIO(3)
NAME
getc_unlocked, getchar_unlocked, putc_unlocked, putchar_unlocked - nonlocking stdio functions
SYNOPSIS
#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 *restrict ptr, size_t size, size_t n,
FILE *restrict stream);
size_t fwrite_unlocked(const void *restrict ptr, size_t size, size_t n,
FILE *restrict stream);
char *fgets_unlocked(char *restrict s, int n, FILE *restrict stream);
int fputs_unlocked(const char *restrict s, FILE *restrict 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 *restrict ws, int n,
FILE *restrict stream);
int fputws_unlocked(const wchar_t *restrict ws,
FILE *restrict 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 <= 2.23: */ _POSIX_C_SOURCE
|| /* Glibc <= 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 <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
fgets_unlocked(), fputs_unlocked(), getwc_unlocked(), getwchar_unlocked(), fgetwc_unlocked(), fputwc_unlocked(), putwchar_unlocked(), fgetws_unlocked(),
fputws_unlocked():
_GNU_SOURCE
DESCRIPTION
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 them‐
selves, and do not test for the presence of locks set by others) and hence are thread-unsafe. See flockfile(3).
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌────────────────────────────────────────┬───────────────┬───────────────────────────────────────────────────────────────────────────────────────────────────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────┼───────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────┤
│getc_unlocked(), putc_unlocked(), │ Thread safety │ MT-Safe race:stream │
│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() │ │ │
├────────────────────────────────────────┼───────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────┤
│getchar_unlocked(), getwchar_unlocked() │ Thread safety │ MT-Unsafe race:stdin │
├────────────────────────────────────────┼───────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────┤
│putchar_unlocked(), putwchar_unlocked() │ Thread safety │ MT-Unsafe race:stdout │
├────────────────────────────────────────┼───────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────┤
│feof_unlocked(), ferror_unlocked(), │ Thread safety │ MT-Safe │
│fileno_unlocked() │ │ │
└────────────────────────────────────────┴───────────────┴───────────────────────────────────────────────────────────────────────────────────────────────────────┘
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)
2021-03-22 UNLOCKED_STDIO(3)