[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
.Fn chmod "const char *path" "mode_t mode"
.Ft int
.Fn fchmod "int fd" "mode_t mode"
.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 fd .
.Fn Chmod
verifies that the process owner (user) either owns
the file specified by
.Fa path
(or
.Fa fd ) ,
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
.Fn Chmod
will fail and the file mode will be unchanged 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 EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.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.
.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.
.El
.Pp
.Fn Fchmod
will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The descriptor is not valid.
.It Bq Er EINVAL
.Fa fd
refers to a socket, not to a file.
.It Bq Er EROFS
The file resides on a read-only file system.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr chmod 1 ,
.Xr open 2 ,
.Xr chown 2 ,
.Xr stat 2 ,
.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
	47	.Fn chmod "const char *path" "mode_t mode"
	48	.Ft int
	49	.Fn fchmod "int fd" "mode_t mode"
	50	.Sh DESCRIPTION
	51	The function
	52	.Fn chmod
	53	sets the file permission bits
	54	of the file
	55	specified by the pathname
	56	.Fa path
	57	to
	58	.Fa mode .
	59	.Fn Fchmod
	60	sets the permission bits of the specified
	61	file descriptor
	62	.Fa fd .
	63	.Fn Chmod
	64	verifies that the process owner (user) either owns
65	the file specified by
66	.Fa path
67	(or
68	.Fa fd ) ,
69	or
70	is the super-user.
71	A mode is created from
72	.Em or'd
73	permission bit masks
74	defined in
75	.Aq Pa sys/stat.h :
76	.Bd -literal -offset indent -compact
77	#define S_IRWXU 0000700 /* RWX mask for owner */
78	#define S_IRUSR 0000400 /* R for owner */
79	#define S_IWUSR 0000200 /* W for owner */
80	#define S_IXUSR 0000100 /* X for owner */
81
82	#define S_IRWXG 0000070 /* RWX mask for group */
83	#define S_IRGRP 0000040 /* R for group */
84	#define S_IWGRP 0000020 /* W for group */
85	#define S_IXGRP 0000010 /* X for group */
86
87	#define S_IRWXO 0000007 /* RWX mask for other */
88	#define S_IROTH 0000004 /* R for other */
89	#define S_IWOTH 0000002 /* W for other */
90	#define S_IXOTH 0000001 /* X for other */
91
92	#define S_ISUID 0004000 /* set user id on execution */
93	#define S_ISGID 0002000 /* set group id on execution */
94	#define S_ISVTX 0001000 /* save swapped text even after use */
95	.Ed
96	.Pp
97	The
98	.Dv ISVTX
99	(the
100	.Em sticky bit )
101	indicates to the system which executable files are shareable (the
102	default) and the system maintains the program text of the files
103	in the swap area. The sticky bit may only be set by the super user
104	on shareable executable files.
105	.Pp
106	If mode
107	.Dv ISVTX
108	(the `sticky bit') is set on a directory,
109	an unprivileged user may not delete or rename
110	files of other users in that directory. The sticky bit may be
111	set by any user on a directory which the user owns or has appropriate
112	permissions.
113	For more details of the properties of the sticky bit, see
114	.Xr sticky 8 .
115	.Pp
116	Writing or changing the owner of a file
117	turns off the set-user-id and set-group-id bits
118	unless the user is the super-user.
119	This makes the system somewhat more secure
120	by protecting set-user-id (set-group-id) files
121	from remaining set-user-id (set-group-id) if they are modified,
122	at the expense of a degree of compatibility.
123	.Sh RETURN VALUES
124	Upon successful completion, a value of 0 is returned.
125	Otherwise, a value of -1 is returned and
126	.Va errno
127	is set to indicate the error.
128	.Sh ERRORS
129	.Fn Chmod
130	will fail and the file mode will be unchanged if:
131	.Bl -tag -width Er
132	.It Bq Er ENOTDIR
133	A component of the path prefix is not a directory.
134	.It Bq Er ENAMETOOLONG
135	A component of a pathname exceeded
136	.Dv {NAME_MAX}
137	characters, or an entire path name exceeded
138	.Dv {PATH_MAX}
139	characters.
140	.It Bq Er ENOENT
141	The named file does not exist.
142	.It Bq Er EACCES
143	Search permission is denied for a component of the path prefix.
144	.It Bq Er ELOOP
145	Too many symbolic links were encountered in translating the pathname.
146	.It Bq Er EPERM
147	The effective user ID does not match the owner of the file and
148	the effective user ID is not the super-user.
149	.It Bq Er EROFS
150	The named file resides on a read-only file system.
151	.It Bq Er EFAULT
152	.Fa Path
153	points outside the process's allocated address space.
154	.It Bq Er EIO
155	An I/O error occurred while reading from or writing to the file system.
156	.El
157	.Pp
158	.Fn Fchmod
159	will fail if:
160	.Bl -tag -width Er
161	.It Bq Er EBADF
162	The descriptor is not valid.
163	.It Bq Er EINVAL
55e303ae	164	.Fa fd
9bccf70c A	165	refers to a socket, not to a file.
	166	.It Bq Er EROFS
	167	The file resides on a read-only file system.
	168	.It Bq Er EIO
	169	An I/O error occurred while reading from or writing to the file system.
	170	.El
	171	.Sh SEE ALSO
	172	.Xr chmod 1 ,
	173	.Xr open 2 ,
	174	.Xr chown 2 ,
	175	.Xr stat 2 ,
	176	.Xr sticky 8
	177	.Sh STANDARDS
	178	The
	179	.Fn chmod
	180	function is expected to conform to
	181	.St -p1003.1-88 .
	182	.Sh HISTORY
	183	The
	184	.Fn fchmod
	185	function call
	186	appeared in
	187	.Bx 4.2 .