STRNCPY(3P) POSIX Programmer's Manual STRNCPY(3P)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.
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.1‐2008 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() func‐
tion shall return the address of the first such NUL character. Other‐
wise, 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 trans‐
ferred, as well as ensure that the s2 and s1 arrays do not overlap.
Character movement is performed differently in different implementa‐
tions. 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 ALSOstrcpy(), wcsncpy()
The Base Definitions volume of POSIX.1‐2008, <string.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 STRNCPY(3P)
