man3/memmem.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     386BSD man pages
  28 .\" Modified Sat Jul 24 18:50:48 1993 by Rik Faith (faith@cs.unc.edu)
  29 .\" Interchanged 'needle' and 'haystack'; added history, aeb, 980113.
  30 .TH MEMMEM 3  2008-12-05 "GNU" "Linux Programmer's Manual"
  31 .SH NAME
  32 memmem \- locate a substring
  33 .SH SYNOPSIS
  34 .nf
  35 .BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
  36 .B #include <string.h>
  37 .sp
  38 .BI "void *memmem(const void *" haystack ", size_t " haystacklen ,
  39 .BI "             const void *" needle ", size_t " needlelen  );
  40 .fi
  41 .SH DESCRIPTION
  42 The
  43 .BR memmem ()
  44 function finds the start of the first occurrence
  45 of the substring
  46 .IR needle
  47 of length
  48 .I needlelen
  49 in the memory
  50 area
  51 .I haystack
  52 of length
  53 .IR haystacklen .
  54 .SH RETURN VALUE
  55 The
  56 .BR memmem ()
  57 function returns a pointer to the beginning of the
  58 substring, or NULL if the substring is not found.
  59 .SH CONFORMING TO
  60 This function is a GNU extension.
  61 .SH BUGS
  62 This function was broken in Linux libraries up to and including libc 5.0.9;
  63 there the
  64 .IR needle
  65 and
  66 .I haystack
  67 arguments were interchanged,
  68 and a pointer to the end of the first occurrence of
  69 .I needle
  70 was returned.
  71
  72 Both old and new libc's have the bug that if
  73 .I needle
  74 is empty,
  75 .I haystack\-1
  76 (instead of
  77 .IR haystack )
  78 is returned.
  79 And glibc 2.0 makes it worse, returning a pointer to the
  80 last byte of
  81 .IR haystack .
  82 This is fixed in glibc 2.1.
  83 .SH SEE ALSO
  84 .BR strstr (3)