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  2019-03-06 "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 .BI "char *strdupa(const char *" s );
  42 .BI "char *strndupa(const char *" s ", size_t " n );
  43 .fi
  44 .PP
  45 .in -4n
  46 Feature Test Macro Requirements for glibc (see
  47 .BR feature_test_macros (7)):
  48 .in
  49 .PP
  50 .PD 0
  51 .ad l
  52 .BR strdup ():
  53 .RS 4
  54 _XOPEN_SOURCE\ >=\ 500
  55 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  56     || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
  57     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  58 .RE
  59 .PP
  60 .BR strndup ():
  61 .RS 4
  62 .TP 4
  63 Since glibc 2.10:
  64 _POSIX_C_SOURCE\ >=\ 200809L
  65 .TP
  66 Before glibc 2.10:
  67 _GNU_SOURCE
  68 .RE
  69 .PP
  70 .BR strdupa (),
  71 .BR strndupa ():
  72 _GNU_SOURCE
  73 .ad
  74 .PD
  75 .SH DESCRIPTION
  76 The
  77 .BR strdup ()
  78 function returns a pointer to a new string which
  79 is a duplicate of the string
  80 .IR s .
  81 Memory for the new string is
  82 obtained with
  83 .BR malloc (3),
  84 and can be freed with
  85 .BR free (3).
  86 .PP
  87 The
  88 .BR strndup ()
  89 function is similar, but copies at most
  90 .I n
  91 bytes.
  92 If
  93 .I s
  94 is longer than
  95 .IR n ,
  96 only
  97 .I n
  98 bytes are copied, and a terminating null byte (\(aq\e0\(aq) is added.
  99 .PP
 100 .BR strdupa ()
 101 and
 102 .BR strndupa ()
 103 are similar, but use
 104 .BR alloca (3)
 105 to allocate the buffer.
 106 They are available only when using the GNU
 107 GCC suite, and suffer from the same limitations described in
 108 .BR alloca (3).
 109 .SH RETURN VALUE
 110 On success, the
 111 .BR strdup ()
 112 function returns a pointer to the duplicated
 113 string.
 114 It returns NULL if insufficient memory was available, with
 115 .I errno
 116 set to indicate the cause of the error.
 117 .SH ERRORS
 118 .TP
 119 .B ENOMEM
 120 Insufficient memory available to allocate duplicate string.
 121 .SH ATTRIBUTES
 122 For an explanation of the terms used in this section, see
 123 .BR attributes (7).
 124 .TS
 125 allbox;
 126 lbw31 lb lb
 127 l l l.
 128 Interface       Attribute       Value
 129 T{
 130 .BR strdup (),
 131 .BR strndup (),
 132 .BR strdupa (),
 133 .br
 134 .BR strndupa ()
 135 T}      Thread safety   MT-Safe
 136 .TE
 137 .sp 1
 138 .SH CONFORMING TO
 139 .\" 4.3BSD-Reno, not (first) 4.3BSD.
 140 .BR strdup ()
 141 conforms to SVr4, 4.3BSD, POSIX.1-2001.
 142 .BR strndup ()
 143 conforms to POSIX.1-2008.
 144 .BR strdupa ()
 145 and
 146 .BR strndupa ()
 147 are GNU extensions.
 148 .SH SEE ALSO
 149 .BR alloca (3),
 150 .BR calloc (3),
 151 .BR free (3),
 152 .BR malloc (3),
 153 .BR realloc (3),
 154 .BR string (3),
 155 .BR wcsdup (3)