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CHMOD(1)		  BSD General Commands Manual		      CHMOD(1)

NAME
     chmod — change file modes

SYNOPSIS
     chmod [-R [-H | -L | -P]] mode file ...

DESCRIPTION
     The chmod utility modifies the file mode bits of the listed files as
     specified by the mode operand.

     The options are as follows:

     -H	     If the -R option is specified, symbolic links on the command line
	     are followed.  (Symbolic links encountered in the tree traversal
	     are not followed.)

     -L	     If the -R option is specified, all symbolic links are followed.

     -P	     If the -R option is specified, no symbolic links are followed.

     -R	     Change the modes of the file hierarchies rooted in the files
	     instead of just the files themselves.

     Symbolic links do not have modes, so unless the -H or -L option is set,
     chmod on a symbolic link always succeeds and has no effect.  The -H, -L
     and -P options are ignored unless the -R option is specified.  In addi‐
     tion, these options override each other and the command's actions are
     determined by the last one specified.

     Only the owner of a file or the super-user is permitted to change the
     mode of a file.

     The chmod utility exits 0 on success, and >0 if an error occurs.

MODES
     Modes may be absolute or symbolic.	 An absolute mode is an octal number
     constructed by or-ing the following values:

	   4000	   set-user-ID-on-execution
	   2000	   set-group-ID-on-execution
	   1000	   sticky bit, see chmod(2)
	   0400	   read by owner
	   0200	   write by owner
	   0100	   execute (or search for directories) by owner
	   0070	   read, write, execute/search by group
	   0007	   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:

	   mode		::= clause [, clause ...]
	   clause	::= [who ...] [action ...] last_action
	   action	::= op [perm ...]
	   last_action	::= op [perm ...]
	   who		::= a | u | g | o
	   op		::= + | - | =
	   perm		::= r | s | t | w | x | X | u | g | o

     The who symbols ``u'', ``g'', and ``o'' specify the user, group, and
     other parts of the mode bits, respectively.  The who symbol ``a'' is
     equivalent to ``ugo''.

     The perm symbols represent the portions of the mode bits as follows:

	   r	   The read bits.
	   s	   The set-user-ID-on-execution and set-group-ID-on-execution
		   bits.
	   t	   The sticky bit.
	   w	   The write bits.
	   x	   The execute/search bits.
	   X	   The execute/search bits if the file is a directory or any
		   of the execute/search bits are set in the original (unmodi‐
		   fied) mode.	Operations with the perm symbol ``X'' are only
		   meaningful in conjunction with the op symbol ``+'', and are
		   ignored in all other cases.
	   u	   The user permission bits in the mode of the original file.
	   g	   The group permission bits in the mode of the original file.
	   o	   The other permission bits in the mode of the original file.

     The op symbols represent the operation performed, as follows:

     +	   If no value is supplied for perm, the ``+'' operation has no
	   effect.  If no value is supplied for who, each permission bit spec‐
	   ified in perm, for which the corresponding bit in the file mode
	   creation mask is clear, is set.  Otherwise, the mode bits repre‐
	   sented by the specified who and perm values are set.

     -	   If no value is supplied for perm, the ``-'' operation has no
	   effect.  If no value is supplied for who, each permission bit spec‐
	   ified in perm, for which the corresponding bit in the file mode
	   creation mask is clear, is cleared.	Otherwise, the mode bits rep‐
	   resented by the specified who and perm values are cleared.

     =	   The mode bits specified by the who 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 who, each permission
	   bit specified in perm, for which the corresponding bit in the file
	   mode creation mask is clear, is set.	 Otherwise, the mode bits rep‐
	   resented by the specified who and perm values are set.

     Each clause specifies one or more operations to be performed on the mode
     bits, and each operation is applied to the mode bits in the order speci‐
     fied.

     Operations upon the other permissions only (specified by the symbol ``o''
     by itself), in combination with the perm symbols ``s'' or ``t'', are
     ignored.

EXAMPLES
     644	   make a file readable by anyone and writable by the owner
		   only.

     go-w	   deny write permission to group and others.

     =rw,+X	   set the read and write permissions to the usual defaults,
		   but retain any execute permissions that are currently set.

     +X		   make a directory or file searchable/executable by everyone
		   if it is already searchable/executable by anyone.

     755
     u=rwx,go=rx
     u=rwx,go=u-w  make a file readable/executable by everyone and writable by
		   the owner only.

     go=	   clear all mode bits for group and others.

     g=u-w	   set the group bits equal to the user bits, but clear the
		   group write bit.

BUGS
     There's no perm option for the naughty bits.

SEE ALSO
     install(1), chmod(2), stat(2), umask(2), fts(3), setmode(3), symlink(7),
     chown(8)

STANDARDS
     The chmod utility is expected to be POSIX 1003.2 compatible with the
     exception of the perm symbols “t” and “X” which are not included in that
     standard.

BSD				March 31, 1994				   BSD
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