STRNCPY(3)                 POSIX Programmer's Manual                STRNCPY(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
       stpncpy, strncpy -- copy fixed length string, returning a pointer to
       the array end

SYNOPSIS
       #include <string.h>

       char *stpncpy(char *restrict s1, const char *restrict s2, size_t _n);
       char *strncpy(char *restrict s1, const char *restrict s2, size_t _n);

DESCRIPTION
       For strncpy(): The functionality described on this reference page is
       aligned with the ISO C standard. Any conflict between the requirements
       described here and the ISO C standard is unintentional. This volume of
       POSIX.1-2017 defers to the ISO C standard.

       The stpncpy() and strncpy() functions shall copy not more than _n bytes
       (bytes that follow a NUL character are not copied) from the array
       pointed to by s2 to the array pointed to by s1.

       If the array pointed to by s2 is a string that is shorter than _n bytes,
       NUL characters shall be appended to the copy in the array pointed to by
       s1, until _n bytes in all are written.

       If copying takes place between objects that overlap, the behavior is
       undefined.

RETURN VALUE
       If a NUL character is written to the destination, the stpncpy()
       function shall return the address of the first such NUL character.
       Otherwise, it shall return &s1[_n].

       The strncpy() function shall return s1.

       No return values are reserved to indicate an error.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       Applications must provide the space in s1 for the _n bytes to be
       transferred, as well as ensure that the s2 and s1 arrays do not
       overlap.

       Character movement is performed differently in different
       implementations. Thus, overlapping moves may yield surprises.

       If there is no NUL character byte in the first _n bytes of the array
       pointed to by s2, the result is not null-terminated.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       strcpy(), wcsncpy()

       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                           STRNCPY(3)
