199 lines
4.4 KiB
Groff
199 lines
4.4 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek and the American National Standards Committee X3,
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.\" on Information Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)strcpy.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd August 9, 2001
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.Dt STRCPY 3
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.Os
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.Sh NAME
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.Nm strcpy , strncpy
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.Nd copy strings
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In string.h
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.Ft char *
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.Fn stpcpy "char *dst" "const char *src"
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.Ft char *
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.Fn strcpy "char * restrict dst" "const char * restrict src"
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.Ft char *
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.Fn strncpy "char * restrict dst" "const char * restrict src" "size_t len"
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.Sh DESCRIPTION
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The
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.Fn stpcpy
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and
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.Fn strcpy
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functions
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copy the string
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.Fa src
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to
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.Fa dst
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(including the terminating
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.Ql \e0
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character.)
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.Pp
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The
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.Fn strncpy
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function copies at most
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.Fa len
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characters from
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.Fa src
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into
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.Fa dst .
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If
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.Fa src
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is less than
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.Fa len
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characters long,
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the remainder of
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.Fa dst
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is filled with
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.Ql \e0
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characters.
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Otherwise,
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.Fa dst
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is
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.Em not
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terminated.
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.Sh RETURN VALUES
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The
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.Fn strcpy
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and
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.Fn strncpy
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functions
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return
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.Fa dst .
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The
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.Fn stpcpy
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function returns a pointer to the terminating
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.Ql \e0
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character of
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.Fa dst .
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.Sh EXAMPLES
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The following sets
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.Va chararray
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to
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.Dq Li abc\e0\e0\e0 :
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.Bd -literal -offset indent
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char chararray[6];
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(void)strncpy(chararray, "abc", sizeof(chararray));
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.Ed
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.Pp
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The following sets
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.Va chararray
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to
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.Dq Li abcdef :
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.Bd -literal -offset indent
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char chararray[6];
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(void)strncpy(chararray, "abcdefgh", sizeof(chararray));
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.Ed
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.Pp
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Note that it does
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.Em not
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.Tn NUL
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terminate
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.Va chararray
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because the length of the source string is greater than or equal
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to the length argument.
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.Pp
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The following copies as many characters from
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.Va input
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to
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.Va buf
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as will fit and
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.Tn NUL
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terminates the result.
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Because
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.Fn strncpy
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does
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.Em not
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guarantee to
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.Tn NUL
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terminate the string itself, this must be done explicitly.
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.Bd -literal -offset indent
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char buf[1024];
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(void)strncpy(buf, input, sizeof(buf) - 1);
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buf[sizeof(buf) - 1] = '\e0';
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.Ed
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.Pp
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This could be better achieved using
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.Xr strlcpy 3 ,
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as shown in the following example:
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.Pp
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.Dl "(void)strlcpy(buf, input, sizeof(buf));"
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.Pp
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Note that because
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.Xr strlcpy 3
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is not defined in any standards, it should
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only be used when portability is not a concern.
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.Sh SECURITY CONSIDERATIONS
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The
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.Fn strcpy
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function is easily misused in a manner which enables malicious users
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to arbitrarily change a running program's functionality through a
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buffer overflow attack.
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(See
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the FSA
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and
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.Sx EXAMPLES . )
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.Sh SEE ALSO
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.Xr bcopy 3 ,
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.Xr memccpy 3 ,
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.Xr memcpy 3 ,
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.Xr memmove 3 ,
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.Xr strlcpy 3
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.Sh STANDARDS
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The
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.Fn strcpy
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and
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.Fn strncpy
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functions
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conform to
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.St -isoC .
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The
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.Fn stpcpy
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function is an MS-DOS and GNUism.
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The
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.Fn stpcpy
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function
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conforms to no standard.
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.Sh HISTORY
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The
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.Fn stpcpy
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function first appeared in
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.Fx 4.4 ,
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coming from 1998-vintage Linux.
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