strndup

Returns a pointer to a null-terminated byte string, which contains copies of at most size bytes from the string pointed to by str . If the null terminator is not encountered in the first size bytes, it is added to the duplicated string.

The returned pointer must be passed to free to avoid a memory leak.

If an error occurs, a null pointer is returned and errno may be set.

As all functions from Dynamic Memory TR, strndup is only guaranteed to be available if __STDC_ALLOC_LIB__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT2__ to the integer constant 1 before including string.h .

Parameters

Return value

A pointer to the newly allocated string, or a null pointer if an error occurred.

Notes

The function is identical to the POSIX strndup except that it is allowed, but not required to set errno on error.

Example

#ifdef __STDC_ALLOC_LIB__
#define __STDC_WANT_LIB_EXT2__ 1
#else
#define _POSIX_C_SOURCE 200809L
#endif
 
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
 
int main(void)
{
    const char *s1 = "String";
    char *s2 = strndup(s1, 2);
    printf("strndup(\"String\", 2) == %s\n", s2);
    free(s2);
}

strndup("String", 2) == St

See also