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  2017-03-13 "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 .PP
  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 ATTRIBUTES
  60 For an explanation of the terms used in this section, see
  61 .BR attributes (7).
  62 .TS
  63 allbox;
  64 lb lb lb
  65 l l l.
  66 Interface       Attribute       Value
  67 T{
  68 .BR memmem ()
  69 T}      Thread safety   MT-Safe
  70 .TE
  71 .SH CONFORMING TO
  72 This function is not specified in POSIX.1,
  73 but is present on a number of other systems.
  74 .SH BUGS
  75 .\" This function was broken in Linux libraries up to and including libc 5.0.9;
  76 .\" there the
  77 .\" .IR needle
  78 .\" and
  79 .\" .I haystack
  80 .\" arguments were interchanged,
  81 .\" and a pointer to the end of the first occurrence of
  82 .\" .I needle
  83 .\" was returned.
  84 .\"
  85 .\" Both old and new libc's have the bug that if
  86 .\" .I needle
  87 .\" is empty,
  88 .\" .I haystack\-1
  89 .\" (instead of
  90 .\" .IR haystack )
  91 .\" is returned.
  92 In glibc 2.0, if
  93 .I needle
  94 is empty,
  95 .BR memmem ()
  96 returns a pointer to the last byte of
  97 .IR haystack .
  98 This is fixed in glibc 2.1.
  99 .SH SEE ALSO
 100 .BR bstring (3),
 101 .BR strstr (3)