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strdup

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

strdup, strndup, strdupa, strndupa - duplicate a string

LIBRARY

Standard C library (libc,~-lc)

SYNOPSIS

#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

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 ([aq][rs]0[aq]) is added. strdupa() and strndupa() are similar, but use alloca(3) to allocate the buffer.

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	M-Safe

STANDARDS

strdup(): strndup() POSIX.-2008.
strdupa(): strndupa() GNU.

HISTORY

strdup(): SVr4, 4.3BS-Reno, POSIX.-2001.
strndup(): POSIX.-2008.
strdupa(): strndupa() GNU.