.\" 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.
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.\" modification, are permitted provided that the following conditions
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.\"    notice, this list of conditions and the following disclaimer in the
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.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
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.\"    may be used to endorse or promote products derived from this software
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.\"     @(#)strcpy.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd August 9, 2001
.Dt STRCPY 3
.Os
.Sh NAME
.Nm strcpy , strncpy
.Nd copy strings
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In string.h
.Ft char *
.Fn strcpy "char *dst" "const char *src"
.Ft char *
.Fn strncpy "char *dst" "const char *src" "size_t len"
.Sh DESCRIPTION
The
.Fn strcpy
function
copies the string
.Fa src
to
.Fa dst
(including the terminating
.Ql \e0
character).
.Pp
The
.Fn strncpy
function copies not more than
.Fa len
characters from
.Fa src
into
.Fa dst ,
appending
.Ql \e0
characters if
.Fa src
is less than
.Fa len
characters long, and
.Em not
terminating
.Fa dst
otherwise.
.Sh RETURN VALUES
The
.Fn strcpy
and
.Fn strncpy
functions
return
.Fa dst .
.Sh EXAMPLES
The following sets
.Va chararray
to
.Dq Li abc\e0\e0\e0 :
.Bd -literal -offset indent
char chararray[6];

(void)strncpy(chararray, "abc", sizeof(chararray));
.Ed
.Pp
The following sets
.Va chararray
to
.Dq Li abcdef :
.Bd -literal -offset indent
char chararray[6];

(void)strncpy(chararray, "abcdefgh", sizeof(chararray));
.Ed
.Pp
Note that it does
.Em not
.Tn NUL
terminate
.Va chararray
because the length of the source string is greater than or equal
to the length parameter.
.Pp
The following copies as many characters from
.Va input
to
.Va buf
as will fit and
.Tn NUL
terminates the result.
Because
.Fn strncpy
does
.Em not
guarantee to
.Tn NUL
terminate the string itself, this must be done explicitly.
.Bd -literal -offset indent
char buf[1024];

(void)strncpy(buf, input, sizeof(buf) - 1);
buf[sizeof(buf) - 1] = '\e0';
.Ed
.Pp
This could be better achieved using
.Xr strlcpy 3 ,
as shown in the following example:
.Pp
.Dl "(void)strlcpy(buf, input, sizeof(buf));"
.Pp
Note that because
.Xr strlcpy 3
is not defined in any standards, it should
only be used when portability is not a concern.
.Sh SECURITY CONSIDERATIONS
The
.Fn strcpy
function is easily misused in a manner which enables malicious users
to arbitrarily change a running program's functionality through a
buffer overflow attack.
(See
the FSA
and
.Sx EXAMPLES . )
.Sh SEE ALSO
.Xr bcopy 3 ,
.Xr memccpy 3 ,
.Xr memcpy 3 ,
.Xr memmove 3 ,
.Xr strlcpy 3
.Rs
.%T "The FreeBSD Security Architecture"
.%J "/usr/share/doc/{to be decided}"
.Re
.Sh STANDARDS
The
.Fn strcpy
and
.Fn strncpy
functions
conform to
.St -isoC .