MEMCHR(3)                           Linux Programmer's Manual                           MEMCHR(3)



NAME
       memchr, memrchr, rawmemchr - scan memory for a character

SYNOPSIS
       #include <string.h>

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

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

       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  inter‐
       preted 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(): it assumes (i.e.,  the  programmer  knows
       for certain) that an instance of c lies somewhere in the memory area starting at the loca‐
       tion pointed to by s, and so performs an optimized search for c (i.e., no use of  a  count
       argument to limit the range of the search).  If an instance of c is not found, the results
       are unpredictable.  The following call is a fast means of locating a string's  terminating
       null byte:

           char *p = rawmemchr(s, '\0');

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, if one is found.   If  no
       matching byte is found, the result is unspecified.

VERSIONS
       rawmemchr() first appeared in glibc in version 2.1.

       memrchr() first appeared in glibc in version 2.2.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The memchr(), memrchr(), and rawmemchr() functions are thread-safe.

CONFORMING TO
       The memchr() function conforms to SVr4, 4.3BSD, C89, C99, POSIX.1-2001.

       The memrchr() function is a GNU extension, available since glibc 2.1.91.

       The rawmemchr() function is a GNU extension, available since glibc 2.1.

SEE ALSO
       ffs(3),  index(3),  rindex(3),  strchr(3),  strpbrk(3),  strrchr(3), strsep(3), strspn(3),
       strstr(3), wmemchr(3)

COLOPHON
       This page is part of release 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.



                                            2014-03-10                                  MEMCHR(3)