memmem(3) - BetterMan

memmem(3)

locate a substring

distropkg manpages-dev@6.9.1-1dataset 2026-04-01T06:19:02Z+debian+ec4110e+mandoc:1.14.6-4

Synopsis

#define _GNU_SOURCE
         /* See feature_test_macros(7) */
#include <string.h>
void *memmem(const void 
haystack
[.
haystacklen
], size_t 
haystacklen
,
             const void 
needle
[.
needlelen
], size_t 
needlelen
);

—

NAME

memmem - locate a substring

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

bash

#define _GNU_SOURCE\n         /* See feature_test_macros(7) */
\n#include <string.h>

bash

void *memmem(const void \nhaystack\n[.\nhaystacklen\n], size_t \nhaystacklen\n,\n
\n             const void \nneedle\n[.\nneedlelen\n], size_t \nneedlelen\n);

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.

ATTRIBUTES

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

Interface	Attribute	Value
memmem ()	Thread safety	MT-Safe

STANDARDS

None.

HISTORY

musl libc 0.9.7; FreeBSD 6.0, OpenBSD 5.4, NetBSD, Illumos.

BUGS

In glibc 2.0, if needle is empty, memmem() returns a pointer to the last byte of haystack. This is fixed in glibc 2.1.