#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
The memrchr() function is like the memchr() function, except that it searches backwards from the end of the n bytes pointed to by s instead of forwards from the beginning.
The rawmemchr() function is similar to memchr(): it assumes (i.e., the programmer knows for certain) that the character c lies somewhere in the string s, and so performs an optimized search for the character c (i.e., no checking for the terminating null byte, or use of an argument, n, to limit the range of the search). If the character c is not in the string s, then rawmemchr() may proceed to search beyond the end of the string, and the result is unspecified. The folowing call is a fast means of locating a string's terminating null byte:
char *p = rawmemchr(s, '\0');
The rawmemchr() function returns a pointer to the matching byte, if one is found. If no matching byte is found, the result is unspecified.
memrchr() first appeared in glibc in version 2.2.
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.