memmem(3)

memmem3

Memory search submemory

Usage

#define _GNU_SOURCE         /* See feature_test_macros(7) */
#include <string.h>  // see memory.h(3head)

void *memmem(size_t hsize, size_t nsize; const void haystack[hsize], size_t hsize, const void needle[nsize], size_t nsize);

Library

Standard C library (libc, -lc)

Overview

The memmem() function finds the start of the first occurrence of the substring needle of size nsize in the memory area haystack of size hsize.

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).

InterfaceAttributeValue
memmem()Thread safetyMT-Safe

Releases

19 releases since Debian 1.1 (Buzz); the text changed 14 times.

  1. 1.1–1.3
  2. 2.0–2.2
  3. 3.0
  4. 3.1
  5. 4.0
  6. 5.0
  7. 6.0
  8. 7
  9. 8
  10. 9
  11. 10
  12. 11
  13. 12
  14. 13
  15. Arch

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.

From man-pages 6.19-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.