man3/strdup.3

   1 '\" t
   2 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   3 .\"
   4 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   5 .\"
   6 .\" References consulted:
   7 .\"     Linux libc source code
   8 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
   9 .\"     386BSD man pages
  10 .\" Modified Sun Jul 25 10:41:34 1993 by Rik Faith (faith@cs.unc.edu)
  11 .\" Modified Wed Oct 17 01:12:26 2001 by John Levon <moz@compsoc.man.ac.uk>
  12 .TH strdup 3 (date) "Linux man-pages (unreleased)"
  13 .SH NAME
  14 strdup, strndup, strdupa, strndupa \- duplicate a string
  15 .SH LIBRARY
  16 Standard C library
  17 .RI ( libc ", " \-lc )
  18 .SH SYNOPSIS
  19 .nf
  20 .B #include <string.h>
  21 .PP
  22 .BI "char *strdup(const char *" s );
  23 .PP
  24 .BI "char *strndup(const char " s [. n "], size_t " n );
  25 .BI "char *strdupa(const char *" s );
  26 .BI "char *strndupa(const char " s [. n "], size_t " n );
  27 .fi
  28 .PP
  29 .RS -4
  30 Feature Test Macro Requirements for glibc (see
  31 .BR feature_test_macros (7)):
  32 .RE
  33 .PP
  34 .BR strdup ():
  35 .nf
  36     _XOPEN_SOURCE >= 500
  37 .\"    || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
  38         || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
  39         || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  40 .fi
  41 .PP
  42 .BR strndup ():
  43 .nf
  44     Since glibc 2.10:
  45         _POSIX_C_SOURCE >= 200809L
  46     Before glibc 2.10:
  47         _GNU_SOURCE
  48 .fi
  49 .PP
  50 .BR strdupa (),
  51 .BR strndupa ():
  52 .nf
  53     _GNU_SOURCE
  54 .fi
  55 .SH DESCRIPTION
  56 The
  57 .BR strdup ()
  58 function returns a pointer to a new string which
  59 is a duplicate of the string
  60 .IR s .
  61 Memory for the new string is
  62 obtained with
  63 .BR malloc (3),
  64 and can be freed with
  65 .BR free (3).
  66 .PP
  67 The
  68 .BR strndup ()
  69 function is similar, but copies at most
  70 .I n
  71 bytes.
  72 If
  73 .I s
  74 is longer than
  75 .IR n ,
  76 only
  77 .I n
  78 bytes are copied, and a terminating null byte (\[aq]\e0\[aq]) is added.
  79 .PP
  80 .BR strdupa ()
  81 and
  82 .BR strndupa ()
  83 are similar, but use
  84 .BR alloca (3)
  85 to allocate the buffer.
  86 .SH RETURN VALUE
  87 On success, the
  88 .BR strdup ()
  89 function returns a pointer to the duplicated
  90 string.
  91 It returns NULL if insufficient memory was available, with
  92 .I errno
  93 set to indicate the error.
  94 .SH ERRORS
  95 .TP
  96 .B ENOMEM
  97 Insufficient memory available to allocate duplicate string.
  98 .SH ATTRIBUTES
  99 For an explanation of the terms used in this section, see
 100 .BR attributes (7).
 101 .TS
 102 allbox;
 103 lbx lb lb
 104 l l l.
 105 Interface       Attribute       Value
 106 T{
 107 .na
 108 .nh
 109 .BR strdup (),
 110 .BR strndup (),
 111 .BR strdupa (),
 112 .BR strndupa ()
 113 T}      Thread safety   MT-Safe
 114 .TE
 115 .sp 1
 116 .SH STANDARDS
 117 .TP
 118 .BR strdup ()
 119 .TQ
 120 .BR strndup ()
 121 POSIX.1-2008.
 122 .TP
 123 .BR strdupa ()
 124 .TQ
 125 .BR strndupa ()
 126 GNU.
 127 .SH HISTORY
 128 .TP
 129 .BR strdup ()
 130 SVr4, 4.3BSD-Reno, POSIX.1-2001.
 131 .TP
 132 .BR strndup ()
 133 POSIX.1-2008.
 134 .TP
 135 .BR strdupa ()
 136 .TQ
 137 .BR strndupa ()
 138 GNU.
 139 .SH SEE ALSO
 140 .BR alloca (3),
 141 .BR calloc (3),
 142 .BR free (3),
 143 .BR malloc (3),
 144 .BR realloc (3),
 145 .BR string (3),
 146 .BR wcsdup (3)