[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
.Fn access "const char *path" "int mode"
.Sh DESCRIPTION
The
.Fn access
function checks the accessibility of the
file named by
.Fa path
for the access permissions indicated by
.Fa mode .
The value of
.Fa mode
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; otherwise
a 0 value is returned.
.Sh ERRORS
Access to the file is denied if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.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 ELOOP
Too many symbolic links were encountered in translating the pathname.
.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 presently being executed.
.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.  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 EIO
An I/O error occurred while reading from or writing to the file system.
.It Bq Er EINVAL
An invalid value was specified for
.Ar mode .
.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
	45	.Fn access "const char *path" "int mode"
	46	.Sh DESCRIPTION
	47	The
	48	.Fn access
	49	function checks the accessibility of the
	50	file named by
	51	.Fa path
	52	for the access permissions indicated by
	53	.Fa mode .
	54	The value of
	55	.Fa mode
	56	is the bitwise inclusive OR of the access permissions to be
	57	checked
	58	.Pf ( Dv R_OK
	59	for read permission,
	60	.Dv W_OK
	61	for write permission and
	62	.Dv X_OK
	63	for execute/search permission) or the existence test,
	64	.Dv F_OK .
65	All components of the pathname
66	.Fa path
67	are checked for access permissions (including
68	.Dv F_OK ) .
69	.Pp
70	The real user ID is used in place of the effective user ID
71	and the real group access list
72	(including the real group ID) are
73	used in place of the effective ID for verifying permission.
74	.Pp
75	Even if a process has appropriate privileges and indicates success for
76	.Dv X_OK ,
77	the file may not actually have execute permission bits set.
78	Likewise for
79	.Dv R_OK
80	and
81	.Dv W_OK .
82	.Sh RETURN VALUES
83	If
84	.Fa path
85	cannot be found or if any of the desired access modes would
86	not be granted, then a -1 value is returned; otherwise
87	a 0 value is returned.
88	.Sh ERRORS
89	Access to the file is denied if:
90	.Bl -tag -width Er
91	.It Bq Er ENOTDIR
92	A component of the path prefix is not a directory.
93	.It Bq Er ENAMETOOLONG
94	A component of a pathname exceeded
95	.Dv {NAME_MAX}
96	characters, or an entire path name exceeded
97	.Dv {PATH_MAX}
98	characters.
99	.It Bq Er ENOENT
100	The named file does not exist.
101	.It Bq Er ELOOP
102	Too many symbolic links were encountered in translating the pathname.
103	.It Bq Er EROFS
104	Write access is requested for a file on a read-only file system.
105	.It Bq Er ETXTBSY
106	Write access is requested for a pure procedure (shared text)
107	file presently being executed.
108	.It Bq Er EACCES
109	Permission bits of the file mode do not permit the requested
110	access, or search permission is denied on a component of the
111	path prefix. The owner of a file has permission checked with
112	respect to the ``owner'' read, write, and execute mode bits,
113	members of the file's group other than the owner have permission
114	checked with respect to the ``group'' mode bits, and all
115	others have permissions checked with respect to the ``other''
116	mode bits.
117	.It Bq Er EFAULT
118	.Fa Path
119	points outside the process's allocated address space.
120	.It Bq Er EIO
121	An I/O error occurred while reading from or writing to the file system.
122	.It Bq Er EINVAL
123	An invalid value was specified for
124	.Ar mode .
125	.El
126	.Sh SEE ALSO
127	.Xr chmod 2 ,
128	.Xr stat 2
129	.Sh STANDARDS
130	The
131	.Fn access
132	function conforms to
133	.St -p1003.1-90 .
134	.Sh CAVEAT
135	.Fn Access
136	is a potential security hole and
137	should never be used.