memmem(3) Library Functions Manual memmem(3)

memmem - locate a substring

Standard C library (libc, -lc)

#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);

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.

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

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

Interface Attribute Value
memmem () Thread safety MT-Safe


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

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.

bstring(3), strstr(3)

2023-03-30 Linux man-pages 6.04