memchr(3) — Linux manual page

memchr(3)               Library Functions Manual               memchr(3)

NAME

       memchr, memrchr, rawmemchr - scan memory for a character

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <string.h>

       void *memchr(const void s[.n], int c, size_t n);
       void *memrchr(const void s[.n], int c, size_t n);

       [[deprecated]] void *rawmemchr(const void *s, int c);

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

       memrchr(), rawmemchr():
           _GNU_SOURCE

DESCRIPTION

       The memchr() function scans the initial n bytes of the memory
       area pointed to by s for the first instance of c.  Both c and the
       bytes of the memory area pointed to by s are interpreted as
       unsigned char.

       The memrchr() function is like the memchr() function, except that
       it searches backward from the end of the n bytes pointed to by s
       instead of forward from the beginning.

       The rawmemchr() function is similar to memchr(), but it assumes
       (i.e., the programmer knows for certain) that an instance of c
       lies somewhere in the memory area starting at the location
       pointed to by s.  If an instance of c is not found, the behavior
       is undefined.  Use either strlen(3) or memchr(3) instead.

RETURN VALUE

       The memchr() and memrchr() functions return a pointer to the
       matching byte or NULL if the character does not occur in the
       given memory area.

       The rawmemchr() function returns a pointer to the matching byte.

ATTRIBUTES

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           │ Attribute     │ Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ memchr(), memrchr(), rawmemchr()    │ Thread safety │ MT-Safe │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       memchr()
              C11, POSIX.1-2008.

       memrchr()
       rawmemchr()
              GNU.

HISTORY

       memchr()
              POSIX.1-2001, C89, SVr4, 4.3BSD.

       memrchr()
              glibc 2.2.

       rawmemchr()
              glibc 2.1.

SEE ALSO

       bstring(3), ffs(3), memmem(3), strchr(3), strpbrk(3), strrchr(3),
       strsep(3), strspn(3), strstr(3), wmemchr(3)

COLOPHON

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Linux man-pages 6.9.1          2024-05-02                      memchr(3)

Pages that refer to this page: bstring(3), ffs(3), memchr(3), strchr(3), strpbrk(3), strsep(3), strspn(3), strstr(3), strtok(3), wmemchr(3), signal-safety(7)

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