STRDUP(3)                  POSIX Programmer's Manual                 STRDUP(3)



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

NAME
       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.

EXAMPLES
       None.

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.

       Implementations are free to malloc() a buffer containing either (size +
       1) bytes or (strnlen( _s, size) + 1) bytes. Applications should not
       assume that strndup() will allocate (size + 1) bytes when strlen( _s) is
       smaller than size.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       free(), wcsdup()

       The Base Definitions volume of POSIX.1-2017, <string.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                            STRDUP(3)
