[apple/xnu.git] / bsd / man / man2 / access.2

.\"	$NetBSD: access.2,v 1.7 1995/02/27 12:31:44 cgd Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" 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.
.\"
.\"     @(#)access.2	8.2 (Berkeley) 4/1/94
.\"
.Dd April 1, 1994
.Dt ACCESS 2
.Os BSD 4
.Sh NAME
.Nm access
.Nd check access permissions of a file or pathname
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fo access
.Fa "const char *path"
.Fa "int amode"
.Fc
.Sh DESCRIPTION
The
.Fn access
function checks the accessibility of the
file named by
.Fa path
for the access permissions indicated by
.Fa amode .
The value of
.Fa amode
is the bitwise inclusive OR of the access permissions to be
checked
.Pf ( Dv R_OK
for read permission,
.Dv W_OK
for write permission and
.Dv X_OK
for execute/search permission) or the existence test,
.Dv F_OK .
All components of the pathname
.Fa path
are checked for access permissions (including
.Dv F_OK ) .
.Pp
The real user ID is used in place of the effective user ID
and the real group access list
(including the real group ID) are
used in place of the effective ID for verifying permission.
.Pp
Even if a process has appropriate privileges and indicates success for
.Dv X_OK ,
the file may not actually have execute permission bits set.
Likewise for
.Dv R_OK
and
.Dv W_OK .
.Sh RETURN VALUES
If
.Fa path
cannot be found
or if any of the desired access modes would not be granted,
then a -1 value is returned and the global integer variable
.Va errno
is set to indicate the error.
Otherwise, a 0 value is returned.
.Sh ERRORS
Access to the file is denied if:
.Bl -tag -width Er
.\" ==========
.It Bq Er EACCES
Permission bits of the file mode do not permit the requested access,
or search permission is denied on a component of the path prefix.
.Pp
The owner of a file has permission checked
with respect to the ``owner'' read, write, and execute mode bits,
members of the file's group other than the owner have permission checked
with respect to the ``group'' mode bits,
and all others have permissions checked
with respect to the ``other'' mode bits.
.\" 
.\" ==========
.It Bq Er EFAULT
.Fa Path
points outside the process's allocated address space.
.It Bq Er EINVAL
An invalid value was specified for
.Ar amode .
.\" ==========
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.\" ==========
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.\" ==========
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 
.Dv {NAME_MAX}
characters, or an entire path name exceeded 
.Dv {PATH_MAX}
characters.
.\" ==========
.It Bq Er ENOENT
The named file does not exist.
.\" ==========
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.\" ==========
.It Bq Er EROFS
Write access is requested for a file on a read-only file system.
.\" ==========
.It Bq Er ETXTBSY
Write access is requested for a pure procedure (shared text)
file that is presently being executed.
.El
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr stat 2
.Sh STANDARDS
The
.Fn access
function conforms to 
.St -p1003.1-90 .
.Sh CAVEAT
.Fn Access
is a potential security hole and
should never be used.
Commit	Line	Data
9bccf70c A	1	.\" $NetBSD: access.2,v 1.7 1995/02/27 12:31:44 cgd Exp $
	2	.\"
	3	.\" Copyright (c) 1980, 1991, 1993
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)access.2 8.2 (Berkeley) 4/1/94
	35	.\"
	36	.Dd April 1, 1994
	37	.Dt ACCESS 2
	38	.Os BSD 4
	39	.Sh NAME
	40	.Nm access
	41	.Nd check access permissions of a file or pathname
	42	.Sh SYNOPSIS
	43	.Fd #include <unistd.h>
	44	.Ft int
2d21ac55 A	45	.Fo access
	46	.Fa "const char *path"
	47	.Fa "int amode"
	48	.Fc
9bccf70c A	49	.Sh DESCRIPTION
	50	The
	51	.Fn access
	52	function checks the accessibility of the
	53	file named by
	54	.Fa path
	55	for the access permissions indicated by
2d21ac55	56	.Fa amode .
9bccf70c	57	The value of
2d21ac55	58	.Fa amode
9bccf70c A	59	is the bitwise inclusive OR of the access permissions to be
	60	checked
	61	.Pf ( Dv R_OK
	62	for read permission,
	63	.Dv W_OK
	64	for write permission and
	65	.Dv X_OK
	66	for execute/search permission) or the existence test,
	67	.Dv F_OK .
	68	All components of the pathname
	69	.Fa path
	70	are checked for access permissions (including
	71	.Dv F_OK ) .
	72	.Pp
	73	The real user ID is used in place of the effective user ID
	74	and the real group access list
	75	(including the real group ID) are
	76	used in place of the effective ID for verifying permission.
	77	.Pp
	78	Even if a process has appropriate privileges and indicates success for
	79	.Dv X_OK ,
	80	the file may not actually have execute permission bits set.
	81	Likewise for
	82	.Dv R_OK
	83	and
	84	.Dv W_OK .
	85	.Sh RETURN VALUES
	86	If
	87	.Fa path
2d21ac55 A	88	cannot be found
	89	or if any of the desired access modes would not be granted,
	90	then a -1 value is returned and the global integer variable
	91	.Va errno
	92	is set to indicate the error.
	93	Otherwise, a 0 value is returned.
9bccf70c A	94	.Sh ERRORS
	95	Access to the file is denied if:
	96	.Bl -tag -width Er
2d21ac55 A	97	.\" ==========
	98	.It Bq Er EACCES
	99	Permission bits of the file mode do not permit the requested access,
	100	or search permission is denied on a component of the path prefix.
	101	.Pp
	102	The owner of a file has permission checked
	103	with respect to the ``owner'' read, write, and execute mode bits,
	104	members of the file's group other than the owner have permission checked
	105	with respect to the ``group'' mode bits,
	106	and all others have permissions checked
	107	with respect to the ``other'' mode bits.
	108	.\"
	109	.\" ==========
	110	.It Bq Er EFAULT
	111	.Fa Path
	112	points outside the process's allocated address space.
	113	.It Bq Er EINVAL
	114	An invalid value was specified for
	115	.Ar amode .
	116	.\" ==========
	117	.It Bq Er EIO
	118	An I/O error occurred while reading from or writing to the file system.
	119	.\" ==========
	120	.It Bq Er ELOOP
	121	Too many symbolic links were encountered in translating the pathname.
	122	.\" ==========
9bccf70c A	123	.It Bq Er ENAMETOOLONG
	124	A component of a pathname exceeded
	125	.Dv {NAME_MAX}
	126	characters, or an entire path name exceeded
	127	.Dv {PATH_MAX}
	128	characters.
2d21ac55	129	.\" ==========
9bccf70c A	130	.It Bq Er ENOENT
9bccf70c A	131	The named file does not exist.
2d21ac55 A	132	.\" ==========
	133	.It Bq Er ENOTDIR
	134	A component of the path prefix is not a directory.
	135	.\" ==========
9bccf70c A	136	.It Bq Er EROFS
9bccf70c A	137	Write access is requested for a file on a read-only file system.
2d21ac55	138	.\" ==========
9bccf70c A	139	.It Bq Er ETXTBSY
9bccf70c A	140	Write access is requested for a pure procedure (shared text)
2d21ac55	141	file that is presently being executed.
9bccf70c A	142	.El
	143	.Sh SEE ALSO
	144	.Xr chmod 2 ,
	145	.Xr stat 2
	146	.Sh STANDARDS
	147	The
	148	.Fn access
	149	function conforms to
	150	.St -p1003.1-90 .
	151	.Sh CAVEAT
	152	.Fn Access
	153	is a potential security hole and
	154	should never be used.