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NetBSD 6.1.5 - man page for chmod (netbsd section 1)

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

NAME
     chmod -- change file modes

SYNOPSIS
     chmod [-R [-H | -L | -P]] [-fh] 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.

     -f      Do not display a diagnostic message or modify the exit status if chmod fails to
	     change the mode of a file.

     -h      If file is symbolic link, the mode of the link is changed.

     The -H, -L and -P options are ignored unless the -R option is specified.  In addition, these
     options override each other and the command's actions are determined by the last one speci-
     fied.

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

EXIT STATUS
     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 exe-
		   cute/search bits are set in the original (unmodified) 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 specified 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 specified in perm, for which the corresponding
	   bit in the file mode creation mask is clear, is cleared.  Otherwise, the mode bits
	   represented 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 speci-
	   fied, 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 represented 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 specified.

     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 exe-
		   cute 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.

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

STANDARDS
     The chmod utility is expected to be IEEE Std 1003.2-1992 (``POSIX.2'') compatible with the
     exception of the perm symbol ``t'' which is not included in that standard.

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

BSD					 January 22, 2010				      BSD


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