NetBSD/lib/libc/string/strcat.3

.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     from: @(#)strcat.3	8.1 (Berkeley) 6/4/93
.\"	$NetBSD: strcat.3,v 1.12 2003/01/07 17:12:54 wiz Exp $
.\"
.Dd August 11, 2002
.Dt STRCAT 3
.Os
.Sh NAME
.Nm strcat ,
.Nm strncat
.Nd concatenate strings
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include \*[Lt]string.h\*[Gt]
.Ft char *
.Fn strcat "char * restrict s" "const char * restrict append"
.Ft char *
.Fn strncat "char * restrict s" "const char * restrict append" "size_t count"
.Sh DESCRIPTION
The
.Fn strcat
and
.Fn strncat
functions
append a copy of the null-terminated string
.Fa append
to the end of the null-terminated string
.Fa s ,
then add a terminating
.Ql \e0 .
The string
.Fa s
must have sufficient space to hold the result.
.Pp
The
.Fn strncat
function
appends not more than
.Fa count
characters where space for the terminating
.Ql \e0
should not be included in
.Fa count .
.Sh RETURN VALUES
The
.Fn strcat
and
.Fn strncat
functions
return the pointer
.Fa s .
.Sh EXAMPLES
The following appends
.Dq Li abc
to
.Dq Li chararray :
.Bd -literal -offset indent
char *letters = "abcdefghi";

(void)strncat(chararray, letters, 3);
.Ed
.Pp
The following example shows how to use
.Fn strncat
safely in conjunction with
.Xr strncpy 3 .
.Bd -literal -offset indent
char buf[BUFSIZ];
char *input, *suffix;

(void)strncpy(buf, input, sizeof(buf) - 1);
buf[sizeof(buf) - 1] = '\e0';
(void)strncat(buf, suffix, sizeof(buf) - 1 - strlen(buf));
.Ed
.Pp
The above will copy as many characters from
.Dq Li input
to
.Dq Li buf
as will fit.
It then appends as many characters from suffix as will fit (or none
if there is no space).
For operations like this, the
.Xr strlcpy 3
and
.Xr strlcat 3
functions are a better choice, as shown below.
.Bd -literal -offset indent
(void)strlcpy(buf, input, sizeof(buf));
(void)strlcat(buf, suffix, sizeof(buf));
.Ed
.Sh SEE ALSO
.Xr bcopy 3 ,
.Xr memccpy 3 ,
.Xr memcpy 3 ,
.Xr memmove 3 ,
.Xr strcpy 3 ,
.Xr strlcat 3 ,
.Xr strlcpy 3
.Sh STANDARDS
The
.Fn strcat
and
.Fn strncat
functions
conform to
.St -isoC99 .