man3/strdup.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified Sun Jul 25 10:41:34 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified Wed Oct 17 01:12:26 2001 by John Levon <moz@compsoc.man.ac.uk>
.TH STRDUP 3  2012-05-10 "GNU" "Linux Programmer's Manual"
.SH NAME
strdup, strndup, strdupa, strndupa \- duplicate a string
.SH SYNOPSIS
.nf
.B #include <string.h>
.sp
.BI "char *strdup(const char *" s );
.sp
.BI "char *strndup(const char *" s ", size_t " n );
.br
.BI "char *strdupa(const char *" s );
.br
.BI "char *strndupa(const char *" s ", size_t " n );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.PD 0
.ad l
.sp
.BR strdup ():
.RS 4
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
.br
|| /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
.RE
.PP
.BR strndup ():
.RS 4
.TP 4
Since glibc 2.10:
POSIX_C_SOURCE\ >=\ 200809L || _XOPEN_SOURCE\ >=\ 700
.TP
Before glibc 2.10:
_GNU_SOURCE
.RE
.PP
.BR strdupa (),
.BR strndupa ():
_GNU_SOURCE
.ad
.PD
.SH DESCRIPTION
The
.BR strdup ()
function returns a pointer to a new string which
is a duplicate of the string \fIs\fP.
Memory for the new string is
obtained with
.BR malloc (3),
and can be freed with
.BR free (3).

The
.BR strndup ()
function is similar, but only copies at most
\fIn\fP bytes.
If \fIs\fP is longer than \fIn\fP, only \fIn\fP
bytes are copied, and a terminating null byte (\(aq\\0\(aq) is added.

.BR strdupa ()
and
.BR strndupa ()
are similar, but use
.BR alloca (3)
to allocate the buffer.
They are only available when using the GNU
GCC suite, and suffer from the same limitations described in
.BR alloca (3).
.SH "RETURN VALUE"
The
.BR strdup ()
function returns a pointer to the duplicated
string, or NULL if insufficient memory was available.
.SH ERRORS
.TP
.B ENOMEM
Insufficient memory available to allocate duplicate string.
.SH "CONFORMING TO"
.\" 4.3BSD-Reno, not (first) 4.3BSD.
.BR strdup ()
conforms to SVr4, 4.3BSD, POSIX.1-2001.
.BR strndup ()
conforms to POSIX.1-2008.
.BR strdupa ()
and
.BR strndupa ()
are GNU extensions.
.SH "SEE ALSO"
.BR alloca (3),
.BR calloc (3),
.BR free (3),
.BR malloc (3),
.BR realloc (3),
.BR string (3),
.BR wcsdup (3)