Linux manual pages Section 3: Subroutines  

Name

strdup, strndup, strdupa, strndupa — duplicate a string

Synopsis

#include <string.h>
char *strdup( const char *s);
 
char *strndup( const char *s,
  size_t n);
 
char *strdupa( const char *s);
 
char *strndupa( const char *s,
  size_t n);
 
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
strdup():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
|| /* Since glibc 2.12: */
_POSIX_C_SOURCE >= 200809L
strndup():
Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700
Before glibc 2.10:
_GNU_SOURCE
strdupa(), strndupa():
_GNU_SOURCE

DESCRIPTION

The strdup() function returns a pointer to a new string which is a duplicate of the string s. Memory for the new string is obtained with malloc(3), and can be freed with free(3).

The strndup() function is similar, but copies at most n bytes. If s is longer than n, only n bytes are copied, and a terminating null byte ('\0') is added.

strdupa() and strndupa() are similar, but use alloca(3) to allocate the buffer. They are available only when using the GNU GCC suite, and suffer from the same limitations described in alloca(3).

RETURN VALUE

On success, the strdup() function returns a pointer to the duplicated string. It returns NULL if insufficient memory was available, with errno set to indicate the cause of the error.

ERRORS

ENOMEM

Insufficient memory available to allocate duplicate string.

CONFORMING TO

strdup() conforms to SVr4, 4.3BSD, POSIX.1-2001. strndup() conforms to POSIX.1-2008. strdupa() and strndupa() are GNU extensions.

SEE ALSO

alloca(3), calloc(3), free(3), malloc(3), realloc(3), string(3), wcsdup(3)

COLOPHON

This page is part of release 3.54 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man−pages/.


  Copyright 1993 David Metcalfe (davidprism.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 (faithcs.unc.edu)
Modified Wed Oct 17 01:12:26 2001 by John Levon <mozcompsoc.man.ac.uk>