1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
136 lines
4.5 KiB
Groff
136 lines
4.5 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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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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.\" @(#)access.2 8.2 (Berkeley) 4/1/94
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.\" $FreeBSD$
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.\"
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.Dd April 1, 1994
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.Dt ACCESS 2
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.Os BSD 4
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.Sh NAME
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.Nm access
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.Nd check access permissions of a file or pathname
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.Sh SYNOPSIS
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.Fd #include <unistd.h>
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.Ft int
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.Fn access "const char *path" "int mode"
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.Sh DESCRIPTION
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The
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.Fn access
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function checks the accessibility of the
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file named by
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.Fa path
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for the access permissions indicated by
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.Fa mode .
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The value of
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.Fa mode
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is the bitwise inclusive OR of the access permissions to be
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checked
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.Pf ( Dv R_OK
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for read permission,
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.Dv W_OK
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for write permission and
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.Dv X_OK
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for execute/search permission) or the existence test,
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.Dv F_OK .
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All components of the pathname
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.Fa path
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are checked for access permissions (including
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.Dv F_OK ) .
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.Pp
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The real user ID is used in place of the effective user ID
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and the real group access list
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(including the real group ID) are
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used in place of the effective ID for verifying permission.
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.Pp
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Even if a process has appropriate privileges and indicates success for
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.Dv X_OK ,
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the file may not actually have execute permission bits set.
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Likewise for
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.Dv R_OK
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and
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.Dv W_OK .
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.Sh RETURN VALUES
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If
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.Fa path
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cannot be found or if any of the desired access modes would
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not be granted, then a -1 value is returned; otherwise
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a 0 value is returned.
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.Sh ERRORS
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Access to the file is denied if:
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.Bl -tag -width Er
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.It Bq Er ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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or an entire path name exceeded 1023 characters.
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.It Bq Er ENOENT
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The named file does not exist.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er EROFS
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Write access is requested for a file on a read-only file system.
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.It Bq Er ETXTBSY
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Write access is requested for a pure procedure (shared text)
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file presently being executed.
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.It Bq Er EACCES
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Permission bits of the file mode do not permit the requested
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access, or search permission is denied on a component of the
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path prefix. The owner of a file has permission checked with
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respect to the ``owner'' read, write, and execute mode bits,
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members of the file's group other than the owner have permission
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checked with respect to the ``group'' mode bits, and all
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others have permissions checked with respect to the ``other''
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mode bits.
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.It Bq Er EFAULT
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.Fa Path
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points outside the process's allocated address space.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to the file system.
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.El
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.Sh SEE ALSO
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.Xr chmod 2 ,
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.Xr stat 2
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.Sh STANDARDS
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The
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.Fn access
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function call is expected to conform to
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.St -p1003.1-90 .
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.Sh CAVEAT
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.Fn Access
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is a potential security hole and
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should never be used.
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.Sh HISTORY
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An
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.Fn access
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function call appeared in
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.At v7 .
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