memmem(3) — Linux manual page

memmem(3)                Library Functions Manual               memmem(3)

NAME         top

       memmem - locate a substring

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #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         top

       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         top

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

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                            │ Attribute     │ Value   │
       ├──────────────────────────────────────┼───────────────┼─────────┤
       │ memmem()                             │ Thread safety │ MT-Safe │
       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS         top

       None.

HISTORY         top

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

BUGS         top

       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         top

       bstring(3), strstr(3)

COLOPHON         top

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Linux man-pages 6.15            2025-06-28                      memmem(3)

Pages that refer to this page: bstring(3),  memchr(3),  strstr(3)

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