.\" Copyright (c) 1990, 1991, 1993
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
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.\"     from: @(#)strcat.3	8.1 (Berkeley) 6/4/93
.\"	$NetBSD: strcat.3,v 1.16 2006/10/16 08:48:45 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
.In string.h
.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 nul-terminated string
.Fa append
to the end of the nul-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 -isoC-99 .