Name

memmem — locate a substring

Synopsis

#define _GNU_SOURCE
#include <string.h>
void *memmem( const void *  haystack,
  size_t   haystacklen,
  const void *  needle,
  size_t   needlelen);

DESCRIPTION

The memmem() function finds the start of the first occurrence of the substring needle of length needlelen in the memory area haystack of length haystacklen.

RETURN VALUE

The memmem() function returns a pointer to the beginning of the substring, or NULL if the substring is not found.

CONFORMING TO

This function is a GNU extension.

BUGS

This function was broken in Linux libraries up to and including libc 5.0.9; there the needle and haystack arguments were interchanged, and a pointer to the end of the first occurrence of needle was returned. Since libc 5.0.9 is still widely used, this is a dangerous function to use.

Both old and new libc's have the bug that if needle is empty haystack−1 (instead of haystack) is returned. And glibc 2.0 makes it worse, and returns a pointer to the last byte of haystack. This is fixed in glibc 2.1.

SEE ALSO

strstr(3), feature_test_macros(7)

COLOPHON

This page is part of release 2.79 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)

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manual page may be incorrect or out-of-date.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.

References consulted:
    Linux libc source code
    386BSD man pages
Modified Sat Jul 24 18:50:48 1993 by Rik Faith (faithcs.unc.edu)
Interchanged 'needle' and 'haystack'; added history, aeb, 980113.