.\" 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. .\" .\" @(#)strcpy.3 8.1 (Berkeley) 6/4/93 .\" $FreeBSD: src/lib/libc/string/strcpy.3,v 1.24 2002/12/19 09:40:24 ru Exp $ .\" .Dd August 9, 2001 .Dt STRCPY 3 .Os .Sh NAME .Nm stpcpy , .Nm strcpy , .Nm strncpy .Nd copy strings .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In string.h .Ft char * .Fo stpcpy .Fa "char *s1" .Fa "const char *s2" .Fc .Ft char * .Fo strcpy .Fa "char *restrict s1" .Fa "const char *restrict s2" .Fc .Ft char * .Fo strncpy .Fa "char *restrict s1" .Fa "const char *restrict s2" .Fa "size_t n" .Fc .Sh DESCRIPTION The .Fn stpcpy and .Fn strcpy functions copy the string .Fa s2 to .Fa s1 (including the terminating .Ql \e0 character). .Pp The .Fn strncpy function copies at most .Fa n characters from .Fa s2 into .Fa s1 . If .Fa s2 is less than .Fa n characters long, the remainder of .Fa s1 is filled with .Ql \e0 characters. Otherwise, .Fa s1 is .Em not terminated. .Pp The source and destination strings should not overlap, as the behavior is undefined. .Sh RETURN VALUES The .Fn strcpy and .Fn strncpy functions return .Fa s1 . The .Fn stpcpy function returns a pointer to the terminating .Ql \e0 character of .Fa s1 . .Sh EXAMPLES The following sets .Va chararray to .Dq Li abc\e0\e0\e0 : .Bd -literal -offset indent char chararray; (void)strncpy(chararray, "abc", sizeof(chararray)); .Ed .Pp The following sets .Va chararray to .Dq Li abcdef : .Bd -literal -offset indent char chararray; (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 argument. .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; (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 .Sh STANDARDS The .Fn strcpy and .Fn strncpy functions conform to .St -isoC . The .Fn stpcpy function is an MS-DOS and GNUism. The .Fn stpcpy function conforms to no standard. .Sh HISTORY The .Fn stpcpy function first appeared in .Fx 4.4 , coming from 1998-vintage Linux.