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.\" @(#)chmod.1 6.15 (Berkeley) 7/23/91
utility modifies the file mode bits of the listed files
The options are as follows:
Traverse a file hierarchy.
For each file that is of type directory,
changes the mode of all files in the file hierarchy below it followed
by the mode of the directory itself.
Symbolic links are not indirected through, nor are their modes altered.
Only the owner of a file or the super-user is permitted to change
utility exits 0 on success, and >0 if an error occurs.
Modes may be absolute or symbolic.
An absolute mode is an octal number constructed by
.Bl -tag -width 6n -compact -offset indent
set-group-ID-on-execution
execute (or search for directories) by owner
read, write, execute/search by group
read, write, execute/search by others
The read, write, and execute/search values for group and others
are encoded as described for owner.
The symbolic mode is described by the following grammar:
.Bd -literal -offset indent
mode ::= clause [, clause ...]
clause ::= [who ...] [action ...] last_action
last_action ::= op [perm ...]
perm ::= r | s | t | w | X | x | u | g | o
symbols ``u'', ``g'', and ``o'' specify the user, group, and other parts
of the mode bits, respectively.
symbol ``a'' is equivalent to ``ugo''.
symbols represent the portions of the mode bits as follows:
.Bl -tag -width Ds -compact -offset indent
The set-user-ID-on-execution and set-group-ID-on-execution bits.
The execute/search bits if the file is a directory or any of the
execute/search bits are set in the original (unmodified) mode.
symbol ``X'' are only meaningful in conjunction with the
symbol ``+'', and it is ignored in all other cases.
symbols represent the operation performed, as follows:
If no value is supplied for
the ``+'' operation has no effect.
If no value is supplied for
each permission bit specified in
for which the corresponding bit in the file mode creation mask
Otherwise, the mode bits represented by the specified
If no value is supplied for
the ``\-'' operation has no effect.
If no value is supplied for
the mode bits represented by
are cleared for the owner, group and other permissions.
Otherwise, the mode bits represented by the specified
The mode bits specified by the
value are cleared, or, if no who value is specified, the owner, group
and other mode bits are cleared.
Then, if no value is supplied for
each permission bit specified in
for which the corresponding bit in the file mode creation mask
Otherwise, the mode bits represented by the specified
specifies one or more operations to be performed on the mode
bits, and each operation is applied to the mode bits in the
Operations upon the other permissions only (specified by the symbol
``o'' by itself), in combination with the
symbols ``s'' or ``t'', are ignored.
.Bl -tag -width "u=rwx,go=u-w" -compact
make a file readable by anyone and writable by the owner only.
deny write permission to group and others.
set the read and write permissions to the usual defaults, but
retain any execute permissions that are currently set.
make a directory or file searchable/executable by everyone if it is
already searchable/executable by anyone.
make a file readable/executable by everyone and writeable by the owner only.
clear all mode bits for group and others.
set the group bits equal to the user bits, but clear the group write bit.
option for the naughty bits.
utility is expected to be
compatible with the exception
which are not included in that standard.