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);
 
[Note] Note
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 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

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

Interface Attribute Value
memchr(), memrchr(), rawmemchr() Thread safety MT-Safe

CONFORMING TO

memchr(): 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 ALSO

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

COLOPHON

This page is part of release 4.07 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/.


  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)
and Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
    <mtk.manpagesgmail.com>

%%%LICENSE_START(VERBATIM)
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
professionally.

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.
%%%LICENSE_END

Modified Mon Apr 12 12:49:57 1993, David Metcalfe
Modified Sat Jul 24 18:56:22 1993, Rik Faith (faithcs.unc.edu)
Modified Wed Feb 20 21:09:36 2002, Ian Redfern (redfernilogica.com)
2008-07-09, mtk, add rawmemchr()