man3/memmem.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .\" References consulted:
   6 .\"     Linux libc source code
   7 .\"     386BSD man pages
   8 .\" Modified Sat Jul 24 18:50:48 1993 by Rik Faith (faith@cs.unc.edu)
   9 .\" Interchanged 'needle' and 'haystack'; added history, aeb, 980113.
  10 .TH MEMMEM 3  2021-03-22 "GNU" "Linux Programmer's Manual"
  11 .SH NAME
  12 memmem \- locate a substring
  13 .SH LIBRARY
  14 Standard C library
  15 .RI ( libc ", " \-lc )
  16 .SH SYNOPSIS
  17 .nf
  18 .BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
  19 .B #include <string.h>
  20 .PP
  21 .BI "void *memmem(const void *" haystack ", size_t " haystacklen ,
  22 .BI "             const void *" needle ", size_t " needlelen  );
  23 .fi
  24 .SH DESCRIPTION
  25 The
  26 .BR memmem ()
  27 function finds the start of the first occurrence
  28 of the substring
  29 .I needle
  30 of length
  31 .I needlelen
  32 in the memory
  33 area
  34 .I haystack
  35 of length
  36 .IR haystacklen .
  37 .SH RETURN VALUE
  38 The
  39 .BR memmem ()
  40 function returns a pointer to the beginning of the
  41 substring, or NULL if the substring is not found.
  42 .SH ATTRIBUTES
  43 For an explanation of the terms used in this section, see
  44 .BR attributes (7).
  45 .ad l
  46 .nh
  47 .TS
  48 allbox;
  49 lbx lb lb
  50 l l l.
  51 Interface       Attribute       Value
  52 T{
  53 .BR memmem ()
  54 T}      Thread safety   MT-Safe
  55 .TE
  56 .hy
  57 .ad
  58 .sp 1
  59 .SH CONFORMING TO
  60 This function is not specified in POSIX.1,
  61 but is present on a number of other systems.
  62 .SH BUGS
  63 .\" This function was broken in Linux libraries up to and including libc 5.0.9;
  64 .\" there the
  65 .\" .IR needle
  66 .\" and
  67 .\" .I haystack
  68 .\" arguments were interchanged,
  69 .\" and a pointer to the end of the first occurrence of
  70 .\" .I needle
  71 .\" was returned.
  72 .\"
  73 .\" Both old and new libc's have the bug that if
  74 .\" .I needle
  75 .\" is empty,
  76 .\" .I haystack\-1
  77 .\" (instead of
  78 .\" .IR haystack )
  79 .\" is returned.
  80 In glibc 2.0, if
  81 .I needle
  82 is empty,
  83 .BR memmem ()
  84 returns a pointer to the last byte of
  85 .IR haystack .
  86 This is fixed in glibc 2.1.
  87 .SH SEE ALSO
  88 .BR bstring (3),
  89 .BR strstr (3)