man3/memmem.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     386BSD man pages
  26 .\" Modified Sat Jul 24 18:50:48 1993 by Rik Faith (faith@cs.unc.edu)
  27 .\" Interchanged `needle' and `haystack'; added history, aeb, 980113.
  28 .TH MEMMEM 3  1998-01-13 "GNU" "Linux Programmer's Manual"
  29 .SH NAME
  30 memmem \- locate a substring
  31 .SH SYNOPSIS
  32 .nf
  33 .B #define _GNU_SOURCE
  34 .br
  35 .B #include <string.h>
  36 .sp
  37 .BI "void *memmem(const void *" haystack ", size_t " haystacklen ,
  38 .in +\w'void *memmem('u
  39 .BI "const void *" needle ", size_t " needlelen  );
  40 .in
  41 .fi
  42 .SH DESCRIPTION
  43 The \fBmemmem\fP() function finds the start of the first occurrence
  44 of the substring \fIneedle\fP of length \fIneedlelen\fP in the memory
  45 area \fIhaystack\fP of length \fIhaystacklen\fP.
  46 .SH "RETURN VALUE"
  47 The \fBmemmem\fP() function returns a pointer to the beginning of the
  48 substring, or NULL if the substring is not found.
  49 .SH "CONFORMING TO"
  50 This function is a GNU extension.
  51 .SH BUGS
  52 This function was broken in Linux libraries up to and including libc 5.0.9;
  53 there the `needle' and `haystack' arguments were interchanged,
  54 and a pointer to the end of the first occurrence of \fIneedle\fP
  55 was returned.  Since libc 5.0.9 is still widely used, this is a
  56 dangerous function to use.
  57 .br
  58 Both old and new libc's have the bug that if \fIneedle\fP is empty
  59 \fIhaystack\fP-1 (instead of \fIhaystack\fP) is returned.
  60 And glibc 2.0 makes it worse, and returns a pointer to the
  61 last byte of `haystack'. This is fixed in glibc 2.1.
  62 .SH "SEE ALSO"
  63 .BR strstr (3)