.\"	$NetBSD: memmem.3,v 1.4 2024/11/01 16:36:58 nia Exp $
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.\" by Perry E. Metzger of Metzger, Dowdeswell & Co. LLC.
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.Dd November 1, 2024
.Dt MEMMEM 3
.Os
.Sh NAME
.Nm memmem
.Nd locate substring in byte string
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In string.h
.Ft void *
.Fn memmem "const void *block" "size_t blen" "const void *pat" "size_t plen"
.Sh DESCRIPTION
The
.Fn memmem
function locates the first occurrence of the binary string
.Fa pat
of size
.Fa plen
bytes in the byte string
.Fa block
of size
.Fa blen
bytes.
.Sh RETURN VALUES
The
.Fn memmem
function returns a pointer to the substring located, or
.Dv NULL
if no such substring exists within
.Fa block .
.Pp
If
.Fa plen
is zero,
.Fa block
is returned, i.e. a zero length
.Fa pat
is deemed to match the start of the string, as with
.Xr strstr 3 .
.Sh SEE ALSO
.Xr bm 3 ,
.Xr memchr 3 ,
.Xr strchr 3 ,
.Xr strstr 3
.Sh STANDARDS
The
.Nm
function conforms to
.St -p1003.1-2024 .
.Sh HISTORY
.Fn memmem
first appeared in the Free Software Foundation's glibc library.