memmem(3)                  Library Functions Manual                  memmem(3)

NAME
       memmem - locate a substring

LIBRARY
       Standard C library (libc, -lc)

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

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

DESCRIPTION
       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).

       +--------------------------------------------+---------------+---------+
       |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.

SEE ALSO
       bstring(3), strstr(3)

Linux man-pages 6.14              2025-05-06                         memmem(3)