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

NAME
     chmod -- change file modes

SYNOPSIS
     chmod [-fhv] [-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 by default.)

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

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

     -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 if chmod could not modify the mode for file.

     -h      If the file is a symbolic link, change the mode of the link itself rather than the
	     file that the link points to.

     -v      Cause chmod to be verbose, showing filenames as the mode is modified.  If the -v
	     flag is specified more than once, the old and new modes of the file will also be
	     printed, in both octal and symbolic notation.

     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.

DIAGNOSTICS
     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 from the
     sum of one or more of the following values:

	   4000    (the set-user-ID-on-execution bit) Executable files with this bit set will run
		   with effective uid set to the uid of the file owner.  Directories with the
		   set-user-id bit set will force all files and sub-directories created in them
		   to be owned by the directory owner and not by the uid of the creating process,
		   if the underlying file system supports this feature: see chmod(2) and the
		   suiddir option to mount(8).
	   2000    (the set-group-ID-on-execution bit) Executable files with this bit set will
		   run with effective gid set to the gid of the file owner.
	   1000    (the sticky bit) See chmod(2) and sticky(8).
	   0400    Allow read by owner.
	   0200    Allow write by owner.
	   0100    For files, allow execution by owner.  For directories, allow the owner to
		   search in the directory.
	   0040    Allow read by group members.
	   0020    Allow write by group members.
	   0010    For files, allow execution by group members.  For directories, allow group
		   members to search in the directory.
	   0004    Allow read by others.
	   0002    Allow write by others.
	   0001    For files, allow execution by others.  For directories allow others to search
		   in the directory.

     For example, the absolute mode that permits read, write and execute by the owner, read and
     execute by group members, read and execute by others, and no set-uid or set-gid behaviour is
     755 (400+200+100+040+010+004+001).

     The symbolic mode is described by the following grammar:

	   mode 	::= clause [, clause ...]
	   clause	::= [who ...] [action ...] action
	   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 original mode of the file.
	   g	   The group permission bits in the original mode of the file.
	   o	   The other permission bits in the original mode of the 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.

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

COMPATIBILITY
     The -v option is non-standard and its use in scripts is not recommended.

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

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

HISTORY
     A chmod command appeared in Version 1 AT&T UNIX.

BSD					  March 31, 1994				      BSD
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