strdup man page

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

strdup, strndup — duplicate a specific number of bytes from a string

Synopsis

#include <string.h>

char *strdup(const char *s);
char *strndup(const char *s, size_t size);

Description

The strdup() function shall return a pointer to a new string, which is a duplicate of the string pointed to by s. The returned pointer can be passed to free(). A null pointer is returned if the new string cannot be created.

The strndup() function shall be equivalent to the strdup() function, duplicating the provided s in a new block of memory allocated as if by using malloc(), with the exception being that strndup() copies at most size plus one bytes into the newly allocated memory, terminating the new string with a NUL character. If the length of s is larger than size, only size bytes shall be duplicated. If size is larger than the length of s, all bytes in s shall be copied into the new memory buffer, including the terminating NUL character. The newly created string shall always be properly terminated.

Return Value

The strdup() function shall return a pointer to a new string on success. Otherwise, it shall return a null pointer and set errno to indicate the error.

Upon successful completion, the strndup() function shall return a pointer to the newly allocated memory containing the duplicated string. Otherwise, it shall return a null pointer and set errno to indicate the error.

Errors

These functions shall fail if:

ENOMEM
Storage space available is insufficient.

The following sections are informative.

Application Usage

For functions that allocate memory as if by malloc(), the application should release such memory when it is no longer required by a call to free(). For strdup() and strndup(), this is the return value.

See Also

free(), wcsdup()

The Base Definitions volume of POSIX.1‐2008, <string.h>

Info

2013 IEEE/The Open Group POSIX Programmer's Manual