memchr(3)                  Library Functions Manual                  memchr(3)

NAME
       memchr, memrchr - scan memory for a character

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #include <string.h>

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

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

       memrchr():
           _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.

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.

ATTRIBUTES
       For an explanation of the terms used in this section, see
       attributes(7).

       +--------------------------------------------+---------------+---------+
       |Interface                                   | Attribute     | Value   |
       +--------------------------------------------+---------------+---------+
       |memchr (), memrchr ()                       | Thread safety | MT-Safe |
       +--------------------------------------------+---------------+---------+
STANDARDS
       memchr()
              C11, POSIX.1-2008.

       memrchr()
              GNU.

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

       memrchr()
              glibc 2.2.

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

Linux man-pages 6.18              2026-02-25                         memchr(3)