[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 ,
.Nm fchmodat
.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
.Ft int
.Fn fchmodat "int fd" "const char *path" "mode_t mode" "int flag"
.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.
.Pp
The
.Fn fchmodat
is equivalent to
.Fn chmod
except in the case where
.Fa path
specifies a relative path.
In this case the file to be changed is determined relative to the directory
associated with the file descriptor
.Fa fd
instead of the current working directory.
The values for the
.Fa flag
are constructed by a bitwise-inclusive OR of flags from the following list, defined
in
.In fcntl.h :
.Bl -tag -width indent
.It Dv AT_SYMLINK_NOFOLLOW
If
.Fa path
names a symbolic link, then the mode of the symbolic link is changed.
.El
.Pp
If
.Fn fchmodat
is passed the special value
.Dv AT_FDCWD
in the
.Fa fd
parameter, the current working directory is used.
If also
.Fa flag
is zero, the behavior is identical to a call to
.Fn chmod .
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
.Pp
In addition to the
.Fn chmod
errors,
.Fn fchmodat
fails if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument does not specify an absolute path and the
.Fa fd
argument is neither
.Fa AT_FDCWD
nor a valid file descriptor open for searching.
.It Bq Er EINVAL
The value of the
.Fa flag
argument is not valid.
.It Bq Er ENOTDIR
The
.Fa path
argument is not an absolute path and
.Fa fd
is neither
.Dv AT_FDCWD
nor a file descriptor associated with a directory.
.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 .
The
.Fn fchmodat
function is expected to conform to POSIX.1-2008 . 
.Sh HISTORY
The
.Fn fchmod
function call
appeared in
.Bx 4.2 .
The
.Fn fchmodat
system call appeared in OS X 10.10
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 ,
fe8ab488 A	41	.Nm fchmod ,
fe8ab488 A	42	.Nm fchmodat
9bccf70c A	43	.Nd change mode of file
	44	.Sh SYNOPSIS
	45	.Fd #include <sys/types.h>
	46	.Fd #include <sys/stat.h>
	47	.Ft int
2d21ac55 A	48	.Fo chmod
	49	.Fa "const char *path"
	50	.Fa "mode_t mode"
	51	.Fc
9bccf70c	52	.Ft int
2d21ac55 A	53	.Fo fchmod
	54	.Fa "int fildes"
	55	.Fa "mode_t mode"
	56	.Fc
fe8ab488 A	57	.Ft int
fe8ab488 A	58	.Fn fchmodat "int fd" "const char *path" "mode_t mode" "int flag"
9bccf70c A	59	.Sh DESCRIPTION
	60	The function
	61	.Fn chmod
	62	sets the file permission bits
	63	of the file
	64	specified by the pathname
	65	.Fa path
	66	to
	67	.Fa mode .
fe8ab488	68	.Fn fchmod
9bccf70c A	69	sets the permission bits of the specified
9bccf70c A	70	file descriptor
2d21ac55	71	.Fa fildes .
fe8ab488	72	.Fn chmod
9bccf70c A	73	verifies that the process owner (user) either owns
	74	the file specified by
	75	.Fa path
	76	(or
2d21ac55	77	.Fa fildes ) ,
9bccf70c A	78	or
9bccf70c A	79	is the super-user.
fe8ab488 A	80	.Pp
	81	The
	82	.Fn fchmodat
	83	is equivalent to
	84	.Fn chmod
	85	except in the case where
	86	.Fa path
	87	specifies a relative path.
	88	In this case the file to be changed is determined relative to the directory
	89	associated with the file descriptor
	90	.Fa fd
	91	instead of the current working directory.
	92	The values for the
	93	.Fa flag
	94	are constructed by a bitwise-inclusive OR of flags from the following list, defined
	95	in
	96	.In fcntl.h :
	97	.Bl -tag -width indent
	98	.It Dv AT_SYMLINK_NOFOLLOW
	99	If
	100	.Fa path
	101	names a symbolic link, then the mode of the symbolic link is changed.
	102	.El
	103	.Pp
	104	If
	105	.Fn fchmodat
	106	is passed the special value
	107	.Dv AT_FDCWD
	108	in the
	109	.Fa fd
	110	parameter, the current working directory is used.
	111	If also
	112	.Fa flag
	113	is zero, the behavior is identical to a call to
	114	.Fn chmod .
9bccf70c A	115	A mode is created from
	116	.Em or'd
	117	permission bit masks
	118	defined in
	119	.Aq Pa sys/stat.h :
	120	.Bd -literal -offset indent -compact
	121	#define S_IRWXU 0000700 /* RWX mask for owner */
	122	#define S_IRUSR 0000400 /* R for owner */
	123	#define S_IWUSR 0000200 /* W for owner */
	124	#define S_IXUSR 0000100 /* X for owner */
	125
	126	#define S_IRWXG 0000070 /* RWX mask for group */
	127	#define S_IRGRP 0000040 /* R for group */
	128	#define S_IWGRP 0000020 /* W for group */
	129	#define S_IXGRP 0000010 /* X for group */
	130
	131	#define S_IRWXO 0000007 /* RWX mask for other */
	132	#define S_IROTH 0000004 /* R for other */
	133	#define S_IWOTH 0000002 /* W for other */
	134	#define S_IXOTH 0000001 /* X for other */
	135
	136	#define S_ISUID 0004000 /* set user id on execution */
	137	#define S_ISGID 0002000 /* set group id on execution */
	138	#define S_ISVTX 0001000 /* save swapped text even after use */
	139	.Ed
	140	.Pp
	141	The
	142	.Dv ISVTX
	143	(the
	144	.Em sticky bit )
	145	indicates to the system which executable files are shareable (the
	146	default) and the system maintains the program text of the files
	147	in the swap area. The sticky bit may only be set by the super user
	148	on shareable executable files.
	149	.Pp
	150	If mode
	151	.Dv ISVTX
	152	(the `sticky bit') is set on a directory,
	153	an unprivileged user may not delete or rename
	154	files of other users in that directory. The sticky bit may be
	155	set by any user on a directory which the user owns or has appropriate
	156	permissions.
	157	For more details of the properties of the sticky bit, see
	158	.Xr sticky 8 .
	159	.Pp
	160	Writing or changing the owner of a file
	161	turns off the set-user-id and set-group-id bits
	162	unless the user is the super-user.
	163	This makes the system somewhat more secure
	164	by protecting set-user-id (set-group-id) files
	165	from remaining set-user-id (set-group-id) if they are modified,
	166	at the expense of a degree of compatibility.
	167	.Sh RETURN VALUES
	168	Upon successful completion, a value of 0 is returned.
	169	Otherwise, a value of -1 is returned and
	170	.Va errno
	171	is set to indicate the error.
	172	.Sh ERRORS
2d21ac55 A	173	The
	174	.Fn chmod
	175	system call will fail and the file mode will be unchanged if:
9bccf70c	176	.Bl -tag -width Er
2d21ac55 A	177	.\" ==========
	178	.It Bq Er EACCES
	179	Search permission is denied for a component of the path prefix.
	180	.\" ==========
	181	.It Bq Er EFAULT
	182	.Fa Path
	183	points outside the process's allocated address space.
	184	.\" ==========
	185	.It Bq Er EINTR
	186	Its execution was interrupted by a signal.
	187	.\" ==========
	188	.It Bq Er EIO
	189	An I/O error occurred while reading from or writing to the file system.
	190	.\" ==========
	191	.It Bq Er ELOOP
	192	Too many symbolic links were encountered in translating the pathname.
	193	This is taken to be indicative of a looping symbolic link.
	194	.\" ==========
9bccf70c A	195	.It Bq Er ENAMETOOLONG
	196	A component of a pathname exceeded
	197	.Dv {NAME_MAX}
	198	characters, or an entire path name exceeded
	199	.Dv {PATH_MAX}
	200	characters.
2d21ac55	201	.\" ==========
9bccf70c A	202	.It Bq Er ENOENT
9bccf70c A	203	The named file does not exist.
2d21ac55 A	204	.\" ==========
	205	.It Bq Er ENOTDIR
	206	A component of the path prefix is not a directory.
	207	.\" ==========
9bccf70c A	208	.It Bq Er EPERM
	209	The effective user ID does not match the owner of the file and
	210	the effective user ID is not the super-user.
2d21ac55	211	.\" ==========
9bccf70c A	212	.It Bq Er EROFS
9bccf70c A	213	The named file resides on a read-only file system.
9bccf70c A	214	.El
9bccf70c A	215	.Pp
2d21ac55	216	.Fn fchmod
9bccf70c A	217	will fail if:
9bccf70c A	218	.Bl -tag -width Er
2d21ac55	219	.\" ==========
9bccf70c	220	.It Bq Er EBADF
2d21ac55 A	221	.Fa fildes
	222	is not a valid file descriptor.
	223	.\" ==========
9bccf70c	224	.It Bq Er EINVAL
2d21ac55	225	.Fa fildes
9bccf70c	226	refers to a socket, not to a file.
2d21ac55 A	227	.\" ==========
	228	.It Bq Er EINVAL
	229	.Fa mode
	230	is not a valid file mode.
	231	.\" ==========
	232	.It Bq Er EINTR
	233	Its execution was interrupted by a signal.
	234	.\" ==========
9bccf70c A	235	.It Bq Er EIO
9bccf70c A	236	An I/O error occurred while reading from or writing to the file system.
2d21ac55 A	237	.\" ==========
	238	.It Bq Er EPERM
	239	The effective user ID does not match the owner of the file and
	240	the effective user ID is not the super-user.
	241	.\" ==========
	242	.It Bq Er EROFS
	243	The file resides on a read-only file system.
9bccf70c	244	.El
fe8ab488 A	245	.Pp
	246	In addition to the
	247	.Fn chmod
	248	errors,
	249	.Fn fchmodat
	250	fails if:
	251	.Bl -tag -width Er
	252	.It Bq Er EBADF
	253	The
	254	.Fa path
	255	argument does not specify an absolute path and the
	256	.Fa fd
	257	argument is neither
	258	.Fa AT_FDCWD
	259	nor a valid file descriptor open for searching.
	260	.It Bq Er EINVAL
	261	The value of the
	262	.Fa flag
	263	argument is not valid.
	264	.It Bq Er ENOTDIR
	265	The
	266	.Fa path
	267	argument is not an absolute path and
	268	.Fa fd
	269	is neither
	270	.Dv AT_FDCWD
	271	nor a file descriptor associated with a directory.
	272	.El
2d21ac55 A	273	.Sh LEGACY SYNOPSIS
	274	.Fd #include <sys/types.h>
	275	.Fd #include <sys/stat.h>
	276	.Pp
	277	The include file
	278	.In sys/types.h
	279	is necessary.
9bccf70c A	280	.Sh SEE ALSO
9bccf70c A	281	.Xr chmod 1 ,
9bccf70c	282	.Xr chown 2 ,
2d21ac55	283	.Xr open 2 ,
9bccf70c	284	.Xr stat 2 ,
2d21ac55	285	.Xr compat 5 ,
9bccf70c A	286	.Xr sticky 8
	287	.Sh STANDARDS
	288	The
	289	.Fn chmod
	290	function is expected to conform to
	291	.St -p1003.1-88 .
fe8ab488 A	292	The
	293	.Fn fchmodat
	294	function is expected to conform to POSIX.1-2008 .
9bccf70c A	295	.Sh HISTORY
	296	The
	297	.Fn fchmod
	298	function call
	299	appeared in
	300	.Bx 4.2 .
fe8ab488 A	301	The
	302	.Fn fchmodat
	303	system call appeared in OS X 10.10