unlocked_stdio(3)                                     Library Functions Manual                                    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-un‐
       safe.  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(),               │ Thread safety │ MT-Unsafe race:stdin                                                   │
       │getwchar_unlocked()               │               │                                                                        │
       ├──────────────────────────────────┼───────────────┼────────────────────────────────────────────────────────────────────────┤
       │putchar_unlocked(),               │ Thread safety │ MT-Unsafe race:stdout                                                  │
       │putwchar_unlocked()               │               │                                                                        │
       ├──────────────────────────────────┼───────────────┼────────────────────────────────────────────────────────────────────────┤
       │feof_unlocked(),                  │ Thread safety │ MT-Safe                                                                │
       │ferror_unlocked(),                │               │                                                                        │
       │fileno_unlocked()                 │               │                                                                        │
       └──────────────────────────────────┴───────────────┴────────────────────────────────────────────────────────────────────────┘

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)

Linux man-pages 6.03                                         2023-02-05                                           unlocked_stdio(3)