man3/strdup.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified Sun Jul 25 10:41:34 1993 by Rik Faith (faith@cs.unc.edu)
  30 .\" Modified Wed Oct 17 01:12:26 2001 by John Levon <moz@compsoc.man.ac.uk>
  31 .TH STRDUP 3  2016-03-15 "GNU" "Linux Programmer's Manual"
  32 .SH NAME
  33 strdup, strndup, strdupa, strndupa \- duplicate a string
  34 .SH SYNOPSIS
  35 .nf
  36 .B #include <string.h>
  37 .PP
  38 .BI "char *strdup(const char *" s );
  39 .PP
  40 .BI "char *strndup(const char *" s ", size_t " n );
  41 .br
  42 .BI "char *strdupa(const char *" s );
  43 .br
  44 .BI "char *strndupa(const char *" s ", size_t " n );
  45 .fi
  46 .PP
  47 .in -4n
  48 Feature Test Macro Requirements for glibc (see
  49 .BR feature_test_macros (7)):
  50 .in
  51 .PP
  52 .PD 0
  53 .ad l
  54 .BR strdup ():
  55 .RS 4
  56 _XOPEN_SOURCE\ >=\ 500
  57 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  58     || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
  59     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  60 .RE
  61 .PP
  62 .BR strndup ():
  63 .RS 4
  64 .TP 4
  65 Since glibc 2.10:
  66 _POSIX_C_SOURCE\ >=\ 200809L
  67 .TP
  68 Before glibc 2.10:
  69 _GNU_SOURCE
  70 .RE
  71 .PP
  72 .BR strdupa (),
  73 .BR strndupa ():
  74 _GNU_SOURCE
  75 .ad
  76 .PD
  77 .SH DESCRIPTION
  78 The
  79 .BR strdup ()
  80 function returns a pointer to a new string which
  81 is a duplicate of the string
  82 .IR s .
  83 Memory for the new string is
  84 obtained with
  85 .BR malloc (3),
  86 and can be freed with
  87 .BR free (3).
  88 .PP
  89 The
  90 .BR strndup ()
  91 function is similar, but copies at most
  92 .I n
  93 bytes.
  94 If
  95 .I s
  96 is longer than
  97 .IR n ,
  98 only
  99 .I n
 100 bytes are copied, and a terminating null byte (\(aq\\0\(aq) is added.
 101 .PP
 102 .BR strdupa ()
 103 and
 104 .BR strndupa ()
 105 are similar, but use
 106 .BR alloca (3)
 107 to allocate the buffer.
 108 They are available only when using the GNU
 109 GCC suite, and suffer from the same limitations described in
 110 .BR alloca (3).
 111 .SH RETURN VALUE
 112 On success, the
 113 .BR strdup ()
 114 function returns a pointer to the duplicated
 115 string.
 116 It returns NULL if insufficient memory was available, with
 117 .I errno
 118 set to indicate the cause of the error.
 119 .SH ERRORS
 120 .TP
 121 .B ENOMEM
 122 Insufficient memory available to allocate duplicate string.
 123 .SH ATTRIBUTES
 124 For an explanation of the terms used in this section, see
 125 .BR attributes (7).
 126 .TS
 127 allbox;
 128 lbw31 lb lb
 129 l l l.
 130 Interface       Attribute       Value
 131 T{
 132 .BR strdup (),
 133 .BR strndup (),
 134 .BR strdupa (),
 135 .br
 136 .BR strndupa ()
 137 T}      Thread safety   MT-Safe
 138 .TE
 139 .sp 1
 140 .SH CONFORMING TO
 141 .\" 4.3BSD-Reno, not (first) 4.3BSD.
 142 .BR strdup ()
 143 conforms to SVr4, 4.3BSD, POSIX.1-2001.
 144 .BR strndup ()
 145 conforms to POSIX.1-2008.
 146 .BR strdupa ()
 147 and
 148 .BR strndupa ()
 149 are GNU extensions.
 150 .SH SEE ALSO
 151 .BR alloca (3),
 152 .BR calloc (3),
 153 .BR free (3),
 154 .BR malloc (3),
 155 .BR realloc (3),
 156 .BR string (3),
 157 .BR wcsdup (3)