xref: /freebsd/bin/chmod/chmod.1 (revision 39beb93c3f8bdbf72a61fda42300b5ebed7390c8)
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32.\"	@(#)chmod.1	8.4 (Berkeley) 3/31/94
33.\" $FreeBSD$
34.\"
35.Dd January 26, 2009
36.Dt CHMOD 1
37.Os
38.Sh NAME
39.Nm chmod
40.Nd change file modes
41.Sh SYNOPSIS
42.Nm
43.Op Fl fhv
44.Op Fl R Op Fl H | L | P
45.Ar mode
46.Ar
47.Sh DESCRIPTION
48The
49.Nm
50utility modifies the file mode bits of the listed files
51as specified by the
52.Ar mode
53operand.
54.Pp
55The options are as follows:
56.Bl -tag -width indent
57.It Fl f
58Do not display a diagnostic message if
59.Nm
60could not modify the mode for
61.Va file ,
62nor modify the exit status to reflect such failures.
63.It Fl H
64If the
65.Fl R
66option is specified, symbolic links on the command line are followed.
67(Symbolic links encountered in the tree traversal are not followed by
68default.)
69.It Fl h
70If the file is a symbolic link, change the mode of the link itself
71rather than the file that the link points to.
72.It Fl L
73If the
74.Fl R
75option is specified, all symbolic links are followed.
76.It Fl P
77If the
78.Fl R
79option is specified, no symbolic links are followed.
80This is the default.
81.It Fl R
82Change the modes of the file hierarchies rooted in the files
83instead of just the files themselves.
84.It Fl v
85Cause
86.Nm
87to be verbose, showing filenames as the mode is modified.
88If the
89.Fl v
90flag is specified more than once, the old and new modes of the file
91will also be printed, in both octal and symbolic notation.
92.El
93.Pp
94The
95.Fl H ,
96.Fl L
97and
98.Fl P
99options are ignored unless the
100.Fl R
101option is specified.
102In addition, these options override each other and the
103command's actions are determined by the last one specified.
104.Pp
105Only the owner of a file or the super-user is permitted to change
106the mode of a file.
107.Sh EXIT STATUS
108.Ex -std
109.Sh MODES
110Modes may be absolute or symbolic.
111An absolute mode is an octal number constructed from the sum of
112one or more of the following values:
113.Pp
114.Bl -tag -width 6n -compact -offset indent
115.It Li 4000
116(the setuid bit).
117Executable files with this bit set
118will run with effective uid set to the uid of the file owner.
119Directories with this bit set will force all files and
120sub-directories created in them to be owned by the directory owner
121and not by the uid of the creating process, if the underlying file
122system supports this feature: see
123.Xr chmod 2
124and the
125.Cm suiddir
126option to
127.Xr mount 8 .
128.It Li 2000
129(the setgid bit).
130Executable files with this bit set
131will run with effective gid set to the gid of the file owner.
132.It Li 1000
133(the sticky bit).
134See
135.Xr chmod 2
136and
137.Xr sticky 8 .
138.It Li 0400
139Allow read by owner.
140.It Li 0200
141Allow write by owner.
142.It Li 0100
143For files, allow execution by owner.
144For directories, allow the owner to
145search in the directory.
146.It Li 0040
147Allow read by group members.
148.It Li 0020
149Allow write by group members.
150.It Li 0010
151For files, allow execution by group members.
152For directories, allow
153group members to search in the directory.
154.It Li 0004
155Allow read by others.
156.It Li 0002
157Allow write by others.
158.It Li 0001
159For files, allow execution by others.
160For directories allow others to
161search in the directory.
162.El
163.Pp
164For example, the absolute mode that permits read, write and execute by
165the owner, read and execute by group members, read and execute by
166others, and no set-uid or set-gid behaviour is 755
167(400+200+100+040+010+004+001).
168.Pp
169The symbolic mode is described by the following grammar:
170.Bd -literal -offset indent
171mode         ::= clause [, clause ...]
172clause       ::= [who ...] [action ...] action
173action       ::= op [perm ...]
174who          ::= a | u | g | o
175op           ::= + | \- | =
176perm         ::= r | s | t | w | x | X | u | g | o
177.Ed
178.Pp
179The
180.Ar who
181symbols ``u'', ``g'', and ``o'' specify the user, group, and other parts
182of the mode bits, respectively.
183The
184.Ar who
185symbol ``a'' is equivalent to ``ugo''.
186.Pp
187The
188.Ar perm
189symbols represent the portions of the mode bits as follows:
190.Pp
191.Bl -tag -width Ds -compact -offset indent
192.It r
193The read bits.
194.It s
195The set-user-ID-on-execution and set-group-ID-on-execution bits.
196.It t
197The sticky bit.
198.It w
199The write bits.
200.It x
201The execute/search bits.
202.It X
203The execute/search bits if the file is a directory or any of the
204execute/search bits are set in the original (unmodified) mode.
205Operations with the
206.Ar perm
207symbol ``X'' are only meaningful in conjunction with the
208.Ar op
209symbol ``+'', and are ignored in all other cases.
210.It u
211The user permission bits in the original mode of the file.
212.It g
213The group permission bits in the original mode of the file.
214.It o
215The other permission bits in the original mode of the file.
216.El
217.Pp
218The
219.Ar op
220symbols represent the operation performed, as follows:
221.Bl -tag -width 4n
222.It +
223If no value is supplied for
224.Ar perm ,
225the ``+'' operation has no effect.
226If no value is supplied for
227.Ar who ,
228each permission bit specified in
229.Ar perm ,
230for which the corresponding bit in the file mode creation mask
231(see
232.Xr umask 2 )
233is clear, is set.
234Otherwise, the mode bits represented by the specified
235.Ar who
236and
237.Ar perm
238values are set.
239.It \&\-
240If no value is supplied for
241.Ar perm ,
242the ``\-'' operation has no effect.
243If no value is supplied for
244.Ar who ,
245each permission bit specified in
246.Ar perm ,
247for which the corresponding bit in the file mode creation mask
248is clear, is cleared.
249Otherwise, the mode bits represented by the specified
250.Ar who
251and
252.Ar perm
253values are cleared.
254.It =
255The mode bits specified by the
256.Ar who
257value are cleared, or, if no
258.Ar who
259value is specified, the owner, group
260and other mode bits are cleared.
261Then, if no value is supplied for
262.Ar who ,
263each permission bit specified in
264.Ar perm ,
265for which the corresponding bit in the file mode creation mask
266is clear, is set.
267Otherwise, the mode bits represented by the specified
268.Ar who
269and
270.Ar perm
271values are set.
272.El
273.Pp
274Each
275.Ar clause
276specifies one or more operations to be performed on the mode
277bits, and each operation is applied to the mode bits in the
278order specified.
279.Pp
280Operations upon the other permissions only (specified by the symbol
281``o'' by itself), in combination with the
282.Ar perm
283symbols ``s'' or ``t'', are ignored.
284.Pp
285The ``w'' permission on directories will permit file creation, relocation,
286and copy into that directory.
287Files created within the directory itself will inherit its group ID.
288.Sh EXAMPLES
289.Bl -tag -width "u=rwx,go=u-w" -compact
290.It Li 644
291make a file readable by anyone and writable by the owner only.
292.Pp
293.It Li go-w
294deny write permission to group and others.
295.Pp
296.It Li =rw,+X
297set the read and write permissions to the usual defaults, but
298retain any execute permissions that are currently set.
299.Pp
300.It Li +X
301make a directory or file searchable/executable by everyone if it is
302already searchable/executable by anyone.
303.Pp
304.It Li 755
305.It Li u=rwx,go=rx
306.It Li u=rwx,go=u-w
307make a file readable/executable by everyone and writable by the owner only.
308.Pp
309.It Li go=
310clear all mode bits for group and others.
311.Pp
312.It Li g=u-w
313set the group bits equal to the user bits, but clear the group write bit.
314.El
315.Sh COMPATIBILITY
316The
317.Fl v
318option is non-standard and its use in scripts is not recommended.
319.Sh SEE ALSO
320.Xr chflags 1 ,
321.Xr install 1 ,
322.Xr setfacl 1 ,
323.Xr chmod 2 ,
324.Xr stat 2 ,
325.Xr umask 2 ,
326.Xr fts 3 ,
327.Xr setmode 3 ,
328.Xr symlink 7 ,
329.Xr chown 8 ,
330.Xr mount 8 ,
331.Xr sticky 8
332.Sh STANDARDS
333The
334.Nm
335utility is expected to be
336.St -p1003.2
337compatible with the exception of the
338.Ar perm
339symbol
340.Dq t
341which is not included in that standard.
342.Sh HISTORY
343A
344.Nm
345command appeared in
346.At v1 .
347.Sh BUGS
348There is no
349.Ar perm
350option for the naughty bits of a horse.
351