.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
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.\" References consulted:
.\"     Linux libc source code
.\"     386BSD man pages
.\" Modified Sat Jul 24 18:50:48 1993 by Rik Faith (faith@cs.unc.edu)
.\" Interchanged `needle' and `haystack'; added history, aeb, 980113.
.TH MEMMEM 3  "January 13, 1998" "GNU" "Linux Programmer's Manual"
.SH NAME
memmem \- locate a substring
.SH SYNOPSIS
.nf
.B #include <string.h>
.sp
.BI "void *memmem(const void *" haystack ", size_t " haystacklen ,
.RS
.BI "const void *" needle ", size_t " needlelen  );
.fi
.SH DESCRIPTION
The \fBmemmem()\fP function finds the start of the first occurrence
of the substring \fIneedle\fP of length \fIneedlelen\fP in the memory
area \fIhaystack\fP of length \fIhaystacklen\fP.
.SH "RETURN VALUE"
The \fBmemmem()\fP function returns a pointer to the beginning of the
substring, or NULL if the substring is not found.
.SH "CONFORMING TO"
This function is a GNU extension.
.SH BUGS
This function was broken in Linux libraries up to and including libc 5.0.9;
there the `needle' and `haystack' arguments were interchanged,
and a pointer to the end of the first occurrence of \fIneedle\fP
was returned.  Since libc 5.0.9 is still widely used, this is a
dangerous function to use.
.br
Both old and new libc's have the bug that if \fIneedle\fP is empty
\fIhaystack\fP-1 (instead of \fIhaystack\fP) is returned.
And glibc (2.0.5) makes it worse, and returns a pointer to the
last byte of `haystack'.
Hopefully this will be fixed. For the time being, \fImemmem\fP()
should not be used with an empty `needle'.
.SH "SEE ALSO"
.BR strstr (3)