'\" et
.TH STRNCPY "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH 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.
.\"
.SH NAME
stpncpy, strncpy
\(em copy fixed length string, returning a pointer to the array end
.SH SYNOPSIS
.LP
.nf
#include <string.h>
.P
char *stpncpy(char *restrict \fIs1\fP, const char *restrict \fIs2\fP, size_t \fIn\fP);
char *strncpy(char *restrict \fIs1\fP, const char *restrict \fIs2\fP, size_t \fIn\fP);
.fi
.SH DESCRIPTION
For
\fIstrncpy\fR():
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\(hy2017 defers to the ISO\ C standard.
.P
The
\fIstpncpy\fR()
and
\fIstrncpy\fR()
functions shall copy not more than
.IR n
bytes (bytes that follow a NUL character are not copied) from the array
pointed to by
.IR s2
to the array pointed to by
.IR s1 .
.P
If the array pointed to by
.IR s2
is a string that is shorter than
.IR n
bytes, NUL characters shall be appended to the copy in the array
pointed to by
.IR s1 ,
until
.IR n
bytes in all are written.
.P
If copying takes place between objects that overlap, the behavior is
undefined.
.SH "RETURN VALUE"
If a NUL character is written to the destination, the
\fIstpncpy\fR()
function shall return the address of the first such NUL character.
Otherwise, it shall return
.IR &s1 [ n ].
.P
The
\fIstrncpy\fR()
function shall return
.IR s1 .
.P
No return values are reserved to indicate an error.
.SH ERRORS
No errors are defined.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
Applications must provide the space in
.IR s1
for the
.IR n
bytes to be transferred, as well as ensure that the
.IR s2
and
.IR s1
arrays do not overlap.
.P
Character movement is performed differently in different
implementations. Thus, overlapping moves may yield surprises.
.P
If there is no NUL character byte in the first
.IR n
bytes of the array pointed to by
.IR s2 ,
the result is not null-terminated.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIstrcpy\fR\^(\|)",
.IR "\fIwcsncpy\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<string.h>\fP"
.\"
.SH 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 .
.PP
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 .