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);
[Note] Note
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:
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:
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


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.


flockfile(3), stdio(3)


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  Copyright (C) 2001 Andries Brouwer <>.

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