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STRDUP(3) Linux Programmer's Manual STRDUP(3)
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);
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
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 error.
ERRORS
ENOMEM Insufficient memory available to allocate duplicate string.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
│strdup(), strndup(), strdupa(), strndupa() │ Thread safety │ MT-Safe │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘
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)
GNU 2021-03-22 STRDUP(3)