memchr(3) — Linux manual page

memchr(3)               Library Functions Manual               memchr(3)

NAME         top

       memchr, memrchr, rawmemchr - scan memory for a character

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #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[.n], int c);

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

       memrchr(), rawmemchr():
           _GNU_SOURCE

DESCRIPTION         top

       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         top

       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         top

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

       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │Interface                             │ Attribute     │ Value   │
       ├──────────────────────────────────────┼───────────────┼─────────┤
       │memchr(), memrchr(), rawmemchr()      │ Thread safety │ MT-Safe │
       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS         top

       memchr()
              C11, POSIX.1-2008.

       memrchr()
       rawmemchr()
              GNU.

HISTORY         top

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

       memrchr()
              glibc 2.2.

       rawmemchr()
              glibc 2.1.

SEE ALSO         top

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

Linux man-pages 6.04           2023-03-30                      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)

HTML rendering created 2023-06-24 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH.