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

.\"	$NetBSD: chmod.2,v 1.7 1995/02/27 12:32:06 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.
.\"
.\"     @(#)chmod.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt CHMOD 2
.Os BSD 4
.Sh NAME
.Nm chmod ,
.Nm fchmod
.Nd change mode of file
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Ft int
.Fo chmod
.Fa "const char *path"
.Fa "mode_t mode"
.Fc
.Ft int
.Fo fchmod
.Fa "int fildes"
.Fa "mode_t mode"
.Fc
.Sh DESCRIPTION
The function
.Fn chmod
sets the file permission bits
of the file
specified by the pathname
.Fa path
to
.Fa mode .
.Fn Fchmod
sets the permission bits of the specified
file descriptor
.Fa fildes .
.Fn Chmod
verifies that the process owner (user) either owns
the file specified by
.Fa path
(or
.Fa fildes ) ,
or
is the super-user.
A mode is created from
.Em or'd
permission bit masks
defined in
.Aq Pa sys/stat.h :
.Bd -literal -offset indent -compact
#define S_IRWXU 0000700    /* RWX mask for owner */
#define S_IRUSR 0000400    /* R for owner */
#define S_IWUSR 0000200    /* W for owner */
#define S_IXUSR 0000100    /* X for owner */

#define S_IRWXG 0000070    /* RWX mask for group */
#define S_IRGRP 0000040    /* R for group */
#define S_IWGRP 0000020    /* W for group */
#define S_IXGRP 0000010    /* X for group */

#define S_IRWXO 0000007    /* RWX mask for other */
#define S_IROTH 0000004    /* R for other */
#define S_IWOTH 0000002    /* W for other */
#define S_IXOTH 0000001    /* X for other */

#define S_ISUID 0004000    /* set user id on execution */
#define S_ISGID 0002000    /* set group id on execution */
#define S_ISVTX 0001000    /* save swapped text even after use */
.Ed
.Pp
The
.Dv ISVTX
(the
.Em sticky bit )
indicates to the system which executable files are shareable (the
default) and the system maintains the program text of the files
in the swap area. The sticky bit may only be set by the super user
on shareable executable files.
.Pp
If mode
.Dv ISVTX
(the `sticky bit') is set on a directory,
an unprivileged user may not delete or rename
files of other users in that directory. The sticky bit may be
set by any user on a directory which the user owns or has appropriate
permissions.
For more details of the properties of the sticky bit, see
.Xr sticky 8 .
.Pp
Writing or changing the owner of a file
turns off the set-user-id and set-group-id bits
unless the user is the super-user.
This makes the system somewhat more secure
by protecting set-user-id (set-group-id) files
from remaining set-user-id (set-group-id) if they are modified,
at the expense of a degree of compatibility.
.Sh RETURN VALUES
Upon successful completion, a value of 0 is returned.
Otherwise, a value of -1 is returned and
.Va errno
is set to indicate the error.
.Sh ERRORS
The
.Fn chmod
system call will fail and the file mode will be unchanged if:
.Bl -tag -width Er
.\" ==========
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.\" ==========
.It Bq Er EFAULT
.Fa Path
points outside the process's allocated address space.
.\" ==========
.It Bq Er EINTR
Its execution was interrupted by a signal.
.\" ==========
.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.
This is taken to be indicative of a looping symbolic link.
.\" ==========
.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 EPERM
The effective user ID does not match the owner of the file and
the effective user ID is not the super-user.
.\" ==========
.It Bq Er EROFS
The named file resides on a read-only file system.
.El
.Pp
.Fn fchmod
will fail if:
.Bl -tag -width Er
.\" ==========
.It Bq Er EBADF
.Fa fildes
is not a valid file descriptor.
.\" ==========
.It Bq Er EINVAL
.Fa fildes
refers to a socket, not to a file.
.\" ==========
.It Bq Er EINVAL
.Fa mode
is not a valid file mode.
.\" ==========
.It Bq Er EINTR
Its execution was interrupted by a signal.
.\" ==========
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.\" ==========
.It Bq Er EPERM
The effective user ID does not match the owner of the file and
the effective user ID is not the super-user.
.\" ==========
.It Bq Er EROFS
The file resides on a read-only file system.
.El
.Sh LEGACY SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Pp
The include file
.In sys/types.h
is necessary.
.Sh SEE ALSO
.Xr chmod 1 ,
.Xr chown 2 ,
.Xr open 2 ,
.Xr stat 2 ,
.Xr compat 5 ,
.Xr sticky 8
.Sh STANDARDS
The
.Fn chmod
function is expected to conform to 
.St -p1003.1-88 .
.Sh HISTORY
The
.Fn fchmod
function call
appeared in
.Bx 4.2 .
Commit	Line	Data
9bccf70c A	1	.\" $NetBSD: chmod.2,v 1.7 1995/02/27 12:32:06 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	.\" @(#)chmod.2 8.1 (Berkeley) 6/4/93
	35	.\"
	36	.Dd June 4, 1993
	37	.Dt CHMOD 2
	38	.Os BSD 4
	39	.Sh NAME
	40	.Nm chmod ,
	41	.Nm fchmod
	42	.Nd change mode of file
	43	.Sh SYNOPSIS
	44	.Fd #include <sys/types.h>
	45	.Fd #include <sys/stat.h>
	46	.Ft int
2d21ac55 A	47	.Fo chmod
	48	.Fa "const char *path"
	49	.Fa "mode_t mode"
	50	.Fc
9bccf70c	51	.Ft int
2d21ac55 A	52	.Fo fchmod
	53	.Fa "int fildes"
	54	.Fa "mode_t mode"
	55	.Fc
9bccf70c A	56	.Sh DESCRIPTION
	57	The function
	58	.Fn chmod
	59	sets the file permission bits
	60	of the file
	61	specified by the pathname
	62	.Fa path
	63	to
	64	.Fa mode .
	65	.Fn Fchmod
	66	sets the permission bits of the specified
	67	file descriptor
2d21ac55	68	.Fa fildes .
9bccf70c A	69	.Fn Chmod
	70	verifies that the process owner (user) either owns
	71	the file specified by
	72	.Fa path
	73	(or
2d21ac55	74	.Fa fildes ) ,
9bccf70c A	75	or
	76	is the super-user.
	77	A mode is created from
	78	.Em or'd
	79	permission bit masks
	80	defined in
	81	.Aq Pa sys/stat.h :
	82	.Bd -literal -offset indent -compact
	83	#define S_IRWXU 0000700 /* RWX mask for owner */
	84	#define S_IRUSR 0000400 /* R for owner */
	85	#define S_IWUSR 0000200 /* W for owner */
	86	#define S_IXUSR 0000100 /* X for owner */
	87
	88	#define S_IRWXG 0000070 /* RWX mask for group */
	89	#define S_IRGRP 0000040 /* R for group */
	90	#define S_IWGRP 0000020 /* W for group */
	91	#define S_IXGRP 0000010 /* X for group */
	92
	93	#define S_IRWXO 0000007 /* RWX mask for other */
	94	#define S_IROTH 0000004 /* R for other */
	95	#define S_IWOTH 0000002 /* W for other */
	96	#define S_IXOTH 0000001 /* X for other */
	97
	98	#define S_ISUID 0004000 /* set user id on execution */
	99	#define S_ISGID 0002000 /* set group id on execution */
	100	#define S_ISVTX 0001000 /* save swapped text even after use */
	101	.Ed
	102	.Pp
	103	The
	104	.Dv ISVTX
	105	(the
	106	.Em sticky bit )
	107	indicates to the system which executable files are shareable (the
	108	default) and the system maintains the program text of the files
	109	in the swap area. The sticky bit may only be set by the super user
	110	on shareable executable files.
	111	.Pp
	112	If mode
	113	.Dv ISVTX
	114	(the `sticky bit') is set on a directory,
	115	an unprivileged user may not delete or rename
	116	files of other users in that directory. The sticky bit may be
	117	set by any user on a directory which the user owns or has appropriate
	118	permissions.
	119	For more details of the properties of the sticky bit, see
	120	.Xr sticky 8 .
	121	.Pp
	122	Writing or changing the owner of a file
	123	turns off the set-user-id and set-group-id bits
	124	unless the user is the super-user.
	125	This makes the system somewhat more secure
	126	by protecting set-user-id (set-group-id) files
	127	from remaining set-user-id (set-group-id) if they are modified,
	128	at the expense of a degree of compatibility.
	129	.Sh RETURN VALUES
	130	Upon successful completion, a value of 0 is returned.
	131	Otherwise, a value of -1 is returned and
	132	.Va errno
	133	is set to indicate the error.
	134	.Sh ERRORS
2d21ac55 A	135	The
	136	.Fn chmod
	137	system call will fail and the file mode will be unchanged if:
9bccf70c	138	.Bl -tag -width Er
2d21ac55 A	139	.\" ==========
	140	.It Bq Er EACCES
	141	Search permission is denied for a component of the path prefix.
	142	.\" ==========
	143	.It Bq Er EFAULT
	144	.Fa Path
	145	points outside the process's allocated address space.
	146	.\" ==========
	147	.It Bq Er EINTR
	148	Its execution was interrupted by a signal.
	149	.\" ==========
	150	.It Bq Er EIO
	151	An I/O error occurred while reading from or writing to the file system.
	152	.\" ==========
	153	.It Bq Er ELOOP
	154	Too many symbolic links were encountered in translating the pathname.
	155	This is taken to be indicative of a looping symbolic link.
	156	.\" ==========
9bccf70c A	157	.It Bq Er ENAMETOOLONG
	158	A component of a pathname exceeded
	159	.Dv {NAME_MAX}
	160	characters, or an entire path name exceeded
	161	.Dv {PATH_MAX}
	162	characters.
2d21ac55	163	.\" ==========
9bccf70c A	164	.It Bq Er ENOENT
9bccf70c A	165	The named file does not exist.
2d21ac55 A	166	.\" ==========
	167	.It Bq Er ENOTDIR
	168	A component of the path prefix is not a directory.
	169	.\" ==========
9bccf70c A	170	.It Bq Er EPERM
	171	The effective user ID does not match the owner of the file and
	172	the effective user ID is not the super-user.
2d21ac55	173	.\" ==========
9bccf70c A	174	.It Bq Er EROFS
9bccf70c A	175	The named file resides on a read-only file system.
9bccf70c A	176	.El
9bccf70c A	177	.Pp
2d21ac55	178	.Fn fchmod
9bccf70c A	179	will fail if:
9bccf70c A	180	.Bl -tag -width Er
2d21ac55	181	.\" ==========
9bccf70c	182	.It Bq Er EBADF
2d21ac55 A	183	.Fa fildes
	184	is not a valid file descriptor.
	185	.\" ==========
9bccf70c	186	.It Bq Er EINVAL
2d21ac55	187	.Fa fildes
9bccf70c	188	refers to a socket, not to a file.
2d21ac55 A	189	.\" ==========
	190	.It Bq Er EINVAL
	191	.Fa mode
	192	is not a valid file mode.
	193	.\" ==========
	194	.It Bq Er EINTR
	195	Its execution was interrupted by a signal.
	196	.\" ==========
9bccf70c A	197	.It Bq Er EIO
9bccf70c A	198	An I/O error occurred while reading from or writing to the file system.
2d21ac55 A	199	.\" ==========
	200	.It Bq Er EPERM
	201	The effective user ID does not match the owner of the file and
	202	the effective user ID is not the super-user.
	203	.\" ==========
	204	.It Bq Er EROFS
	205	The file resides on a read-only file system.
9bccf70c	206	.El
2d21ac55 A	207	.Sh LEGACY SYNOPSIS
	208	.Fd #include <sys/types.h>
	209	.Fd #include <sys/stat.h>
	210	.Pp
	211	The include file
	212	.In sys/types.h
	213	is necessary.
9bccf70c A	214	.Sh SEE ALSO
9bccf70c A	215	.Xr chmod 1 ,
9bccf70c	216	.Xr chown 2 ,
2d21ac55	217	.Xr open 2 ,
9bccf70c	218	.Xr stat 2 ,
2d21ac55	219	.Xr compat 5 ,
9bccf70c A	220	.Xr sticky 8
	221	.Sh STANDARDS
	222	The
	223	.Fn chmod
	224	function is expected to conform to
	225	.St -p1003.1-88 .
	226	.Sh HISTORY
	227	The
	228	.Fn fchmod
	229	function call
	230	appeared in
	231	.Bx 4.2 .