xref: /freebsd/bin/chmod/chmod.1 (revision 7f3dea244c40159a41ab22da77a434d7c5b5e85a)
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35.\"	@(#)chmod.1	8.4 (Berkeley) 3/31/94
36.\" $FreeBSD$
37.\"
38.Dd March 31, 1994
39.Dt CHMOD 1
40.Os
41.Sh NAME
42.Nm chmod
43.Nd change file modes
44.Sh SYNOPSIS
45.Nm chmod
46.Oo
47.Fl f
48.Fl R
49.Op Fl H | Fl L | Fl P
50.Oc
51.Ar mode
52.Ar file ...
53.Sh DESCRIPTION
54The
55.Nm
56utility modifies the file mode bits of the listed files
57as specified by the
58.Ar mode
59operand.
60.Pp
61The options are as follows:
62.Bl -tag -width Ds
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.)
68.It Fl L
69If the
70.Fl R
71option is specified, all symbolic links are followed.
72.It Fl P
73If the
74.Fl R
75option is specified, no symbolic links are followed.
76.It Fl R
77Change the modes of the file hierarchies rooted in the files
78instead of just the files themselves.
79.It Fl f
80Do not display a diagnostic message if
81.Nm
82could not modify the mode for
83.Va file .
84.El
85.Pp
86Symbolic links do not have modes, so unless the
87.Fl H
88or
89.Fl L
90option is set,
91.Nm
92on a symbolic link always succeeds and has no effect.
93The
94.Fl H ,
95.Fl L
96and
97.Fl P
98options are ignored unless the
99.Fl R
100option is specified.
101In addition, these options override each other and the
102command's actions are determined by the last one specified.
103.Pp
104Only the owner of a file or the super-user is permitted to change
105the mode of a file.
106.Sh DIAGNOSTICS
107The
108.Nm
109utility exits 0 on success, and >0 if an error occurs.
110.Sh MODES
111Modes may be absolute or symbolic.
112An absolute mode is an octal number constructed from the sum of
113one or more of the following values:
114.Pp
115.Bl -tag -width 6n -compact -offset indent
116.It Li 4000
117(the set-user-ID-on-execution bit) Executable files with this bit set
118will run with effective uid set to the uid of the file owner.
119Directories with the set-user-id 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.Ar suiddir
126option to
127.Xr mount 8 .
128.It Li 2000
129(the set-group-ID-on-execution bit)  Executable files with this bit set
130will run with effective gid set to the gid of the file owner.
131.It Li 1000
132(the sticky bit)
133When set on a directory, unprivileged users can delete and rename
134only those files in the directory that are owned by them, regardless of
135the permissions on the directory.  Under FreeBSD, the sticky bit is
136ignored for executable files and may only be set for directories (see
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.  For directories, allow the owner to
144search in the directory.
145.It Li 0040
146Allow read by group members.
147.It Li 0020
148Allow write by group members.
149.It Li 0010
150For files, allow execution by group members.  For directories, allow
151group members to search in the directory.
152.It Li 0004
153Allow read by others.
154.It Li 0002
155Allow write by others.
156.It Li 0001
157For files, allow execution by others.  For directories allow others to
158search in the directory.
159.El
160.Pp
161For example, the absolute mode that permits read, write and execute by
162the owner, read and execute by group members, read and execute by
163others, and no set-uid or set-gid behaviour is 755
164(400+200+100+040+010+004+001).
165.Pp
166The symbolic mode is described by the following grammar:
167.Bd -literal -offset indent
168mode         ::= clause [, clause ...]
169clause       ::= [who ...] [action ...] last_action
170action       ::= op [perm ...]
171last_action  ::= op [perm ...]
172who          ::= a | u | g | o
173op           ::= + | \- | =
174perm         ::= r | s | t | w | x | X | u | g | o
175.Ed
176.Pp
177The
178.Ar who
179symbols ``u'', ``g'', and ``o'' specify the user, group, and other parts
180of the mode bits, respectively.
181The
182.Ar who
183symbol ``a'' is equivalent to ``ugo''.
184.Pp
185.ne 1i
186The
187.Ar perm
188symbols represent the portions of the mode bits as follows:
189.Pp
190.Bl -tag -width Ds -compact -offset indent
191.It r
192The read bits.
193.It s
194The set-user-ID-on-execution and set-group-ID-on-execution bits.
195.It t
196The sticky bit.
197.It w
198The write bits.
199.It x
200The execute/search bits.
201.It X
202The execute/search bits if the file is a directory or any of the
203execute/search bits are set in the original (unmodified) mode.
204Operations with the
205.Ar perm
206symbol ``X'' are only meaningful in conjunction with the
207.Ar op
208symbol ``+'', and are ignored in all other cases.
209.It u
210The user permission bits in the mode of the original file.
211.It g
212The group permission bits in the mode of the original file.
213.It o
214The other permission bits in the mode of the original file.
215.El
216.Pp
217The
218.Ar op
219symbols represent the operation performed, as follows:
220.Bl -tag -width 4n
221.It +
222If no value is supplied for
223.Ar perm ,
224the ``+'' operation has no effect.
225If no value is supplied for
226.Ar who ,
227each permission bit specified in
228.Ar perm ,
229for which the corresponding bit in the file mode creation mask
230is clear, is set.
231Otherwise, the mode bits represented by the specified
232.Ar who
233and
234.Ar perm
235values are set.
236.It \&\-
237If no value is supplied for
238.Ar perm ,
239the ``\-'' operation has no effect.
240If no value is supplied for
241.Ar who ,
242each permission bit specified in
243.Ar perm ,
244for which the corresponding bit in the file mode creation mask
245is clear, is cleared.
246Otherwise, the mode bits represented by the specified
247.Ar who
248and
249.Ar perm
250values are cleared.
251.It =
252The mode bits specified by the
253.Ar who
254value are cleared, or, if no who value is specified, the owner, group
255and other mode bits are cleared.
256Then, if no value is supplied for
257.Ar who ,
258each permission bit specified in
259.Ar perm ,
260for which the corresponding bit in the file mode creation mask
261is clear, is set.
262Otherwise, the mode bits represented by the specified
263.Ar who
264and
265.Ar perm
266values are set.
267.El
268.Pp
269Each
270.Ar clause
271specifies one or more operations to be performed on the mode
272bits, and each operation is applied to the mode bits in the
273order specified.
274.Pp
275Operations upon the other permissions only (specified by the symbol
276``o'' by itself), in combination with the
277.Ar perm
278symbols ``s'' or ``t'', are ignored.
279.Sh EXAMPLES
280.Bl -tag -width "u=rwx,go=u-w" -compact
281.It Li 644
282make a file readable by anyone and writable by the owner only.
283.Pp
284.It Li go-w
285deny write permission to group and others.
286.Pp
287.It Li =rw,+X
288set the read and write permissions to the usual defaults, but
289retain any execute permissions that are currently set.
290.Pp
291.It Li +X
292make a directory or file searchable/executable by everyone if it is
293already searchable/executable by anyone.
294.Pp
295.It Li 755
296.It Li u=rwx,go=rx
297.It Li u=rwx,go=u-w
298make a file readable/executable by everyone and writable by the owner only.
299.Pp
300.It Li go=
301clear all mode bits for group and others.
302.Pp
303.It Li g=u-w
304set the group bits equal to the user bits, but clear the group write bit.
305.El
306.Sh BUGS
307There's no
308.Ar perm
309option for the naughty bits.
310.Sh SEE ALSO
311.Xr chflags 1 ,
312.Xr install 1 ,
313.Xr chmod 2 ,
314.Xr stat 2 ,
315.Xr umask 2 ,
316.Xr fts 3 ,
317.Xr setmode 3 ,
318.Xr symlink 7 ,
319.Xr chown 8 ,
320.Xr mount 8 ,
321.Xr sticky 8
322.Sh STANDARDS
323The
324.Nm
325utility is expected to be
326.St -p1003.2
327compatible with the exception of the
328.Ar perm
329symbols
330.Dq t
331and
332.Dq X
333which are not included in that standard.
334.Sh HISTORY
335A
336.Nm
337command appeared in
338.At v1 .
339