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 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(): 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, and so per‐
forms 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.
VERSIONSrawmemchr() first appeared in glibc in version 2.1.
memrchr() first appeared in glibc in version 2.2.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├─────────────────────────────────┼───────────────┼─────────┤
│memchr(), memrchr(), rawmemchr() │ Thread safety │ MT-Safe │
└─────────────────────────────────┴───────────────┴─────────┘
CONFORMING TOmemchr(): POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
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 ALSObstring(3), ffs(3), index(3), memmem(3), rindex(3), strchr(3), strp‐
brk(3), strrchr(3), strsep(3), strspn(3), strstr(3), wmemchr(3)COLOPHON
This page is part of release 4.14 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
https://www.kernel.org/doc/man-pages/.
2017-09-15 MEMCHR(3)
