usr/src/lib/libc/sys/access.2

.\" Copyright (c) 1980 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)access.2	6.2 (Berkeley) %G%
.\"
.TH ACCESS 2 ""
.UC 4
.SH NAME
access \- determine accessibility of file
.SH SYNOPSIS
.nf
.ft B
#include <sys/file.h>
.PP
.ft B
.ta 1.25i 1.6i
#define R_OK	4	/* test for read permission */
#define W_OK	2	/* test for write permission */
#define X_OK	1	/* test for execute (search) permission */
#define F_OK	0	/* test for presence of file */
.PP
.ft B
accessible = access(path, mode)
int accessible;
char *path;
int mode;
.ft R
.fi
.SH DESCRIPTION
.I Access
checks the given
file
.I path
for accessibility according to
.IR mode ,
which is an inclusive or of the bits
R_OK,
W_OK
and
X_OK.
Specifying
.I mode
as F_OK (i.e. 0)
tests whether the directories leading to the file can be
searched and the file exists.
.PP
The real user ID and the group access list
(including the real group ID) are
used in verifying permission, so this call
is useful to set-UID programs.
.PP
Notice that only access bits are checked.
A directory may be indicated as writable by
.IR access ,
but an attempt to open it for writing will fail
(although files may be created there);
a file may look executable, but
.I execve
will fail unless it is in proper format.
.SH "RETURN VALUE
If
.I 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 one or more of the following are true:
.TP 15
[ENOTDIR]
A component of the path prefix is not a directory.
.TP 15
[ENOENT]
The argument path name was too long.
.TP 15
[ENOENT]
Read, write, or execute (search) permission is requested for a null
path name or the named file does not exist.
.TP 15
[EPERM]
The argument contains a byte with the high-order bit set.
.TP 15
[ELOOP]
Too many symbolic links were encountered in translating the pathname.
.TP 15
[EROFS]
Write access is requested for a file on a read-only file system.
.TP 15
[ETXTBSY]
Write access is requested for a pure procedure (shared text)
file that is being executed.
.TP 15
[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.
.TP 15
[EFAULT]
.I Path
points outside the process's allocated address space.
.SH "SEE ALSO
chmod(2), stat(2)
Commit	Line	Data
	1	.\" Copyright (c) 1980 Regents of the University of California.
	2	.\" All rights reserved. The Berkeley software License Agreement
	3	.\" specifies the terms and conditions for redistribution.
	4	.\"
	5	.\" @(#)access.2 6.2 (Berkeley) %G%
	6	.\"
	7	.TH ACCESS 2 ""
	8	.UC 4
	9	.SH NAME
	10	access \- determine accessibility of file
	11	.SH SYNOPSIS
	12	.nf
	13	.ft B
	14	#include <sys/file.h>
	15	.PP
	16	.ft B
	17	.ta 1.25i 1.6i
	18	#define R_OK 4 /* test for read permission */
	19	#define W_OK 2 /* test for write permission */
	20	#define X_OK 1 /* test for execute (search) permission */
	21	#define F_OK 0 /* test for presence of file */
	22	.PP
	23	.ft B
	24	accessible = access(path, mode)
	25	int accessible;
	26	char *path;
	27	int mode;
	28	.ft R
	29	.fi
	30	.SH DESCRIPTION
	31	.I Access
	32	checks the given
	33	file
	34	.I path
	35	for accessibility according to
	36	.IR mode ,
	37	which is an inclusive or of the bits
	38	R_OK,
	39	W_OK
	40	and
	41	X_OK.
	42	Specifying
	43	.I mode
	44	as F_OK (i.e. 0)
	45	tests whether the directories leading to the file can be
	46	searched and the file exists.
	47	.PP
	48	The real user ID and the group access list
	49	(including the real group ID) are
	50	used in verifying permission, so this call
	51	is useful to set-UID programs.
	52	.PP
	53	Notice that only access bits are checked.
	54	A directory may be indicated as writable by
	55	.IR access ,
	56	but an attempt to open it for writing will fail
	57	(although files may be created there);
	58	a file may look executable, but
	59	.I execve
	60	will fail unless it is in proper format.
	61	.SH "RETURN VALUE
	62	If
	63	.I path
	64	cannot be found or if any of the desired access modes would
	65	not be granted, then a \-1 value is returned; otherwise
	66	a 0 value is returned.
	67	.SH "ERRORS
	68	Access to the file is denied if one or more of the following are true:
	69	.TP 15
	70	[ENOTDIR]
	71	A component of the path prefix is not a directory.
	72	.TP 15
	73	[ENOENT]
	74	The argument path name was too long.
	75	.TP 15
	76	[ENOENT]
	77	Read, write, or execute (search) permission is requested for a null
	78	path name or the named file does not exist.
	79	.TP 15
	80	[EPERM]
	81	The argument contains a byte with the high-order bit set.
	82	.TP 15
	83	[ELOOP]
	84	Too many symbolic links were encountered in translating the pathname.
	85	.TP 15
	86	[EROFS]
	87	Write access is requested for a file on a read-only file system.
	88	.TP 15
	89	[ETXTBSY]
	90	Write access is requested for a pure procedure (shared text)
	91	file that is being executed.
	92	.TP 15
	93	[EACCES]
	94	Permission bits of the file mode do not permit the requested
	95	access; or search permission is denied on a component of the
	96	path prefix. The owner of a file has permission checked with
	97	respect to the ``owner'' read, write, and execute mode bits,
	98	members of the file's group other than the owner have permission
	99	checked with respect to the ``group'' mode bits, and all
	100	others have permissions checked with respect to the ``other''
	101	mode bits.
	102	.TP 15
	103	[EFAULT]
	104	.I Path
	105	points outside the process's allocated address space.
	106	.SH "SEE ALSO
	107	chmod(2), stat(2)