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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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strdup(3) Library Functions Manual strdup(3)
strdup, strndup, strdupa, strndupa - duplicate a string
Standard C library (libc, -lc)
#include <string.h>
char *strdup(const char *s);
char *strndup(size_t n;
const char s[n], size_t n);
char *strdupa(const char *s);
char *strndupa(size_t n;
const char s[n], size_t n);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
strdup():
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
strndup():
Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L
Before glibc 2.10:
_GNU_SOURCE
strdupa(), strndupa():
_GNU_SOURCE
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.
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 error.
ENOMEM Insufficient memory available to allocate duplicate string.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ strdup(), strndup(), strdupa(), │ Thread safety │ MT-Safe │
│ strndupa() │ │ │
└──────────────────────────────────────┴───────────────┴─────────┘
strdup()
strndup()
POSIX.1-2008.
strdupa()
strndupa()
GNU.
strdup()
SVr4, 4.3BSD-Reno, POSIX.1-2001.
strndup()
POSIX.1-2008.
strdupa()
strndupa()
GNU.
alloca(3), calloc(3), free(3), malloc(3), realloc(3), string(3),
wcsdup(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-06-28 strdup(3)
Pages that refer to this page: alloca(3), ldap_memory(3), pmdadaemon(3), pmdafetch(3), pmfault(3), pmtraversepmns(3), strcpy(3), string(3), wcsdup(3), string_copying(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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