UNLOCKED_STDIO(3)

NAME
getc_unlocked, getchar_unlocked, putc_unlocked, putchar_unlocked - nonlocking stdio functions

LIBRARY
Standard C library (libc, -lc)

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 ptr[restrict .size * .n],
                      size_t size, size_t n,
                      FILE *restrict stream);
size_t fwrite_unlocked(const void ptr[restrict .size * .n],
                      size_t size, size_t n,
                      FILE *restrict stream);

char *fgets_unlocked(char s[restrict .n], 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 ws[restrict .n], 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():
    /* 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 >= 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 themselves, 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
 | Thread safety | MT-Safe race:stream
 | Thread safety | MT-Unsafe race:stdin
 | Thread safety | MT-Unsafe race:stdout
 | Thread safety | MT-Safe

STANDARDS
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)