SYNOPSIS

       chmod [OPTION]... MODE[,MODE]... FILE...
       chmod [OPTION]... OCTAL-MODE FILE...
       chmod [OPTION]... --reference=RFILE FILE...

DESCRIPTION

       This manual page documents the GNU version of chmod.  chmod changes the
       file mode bits of each given file  according  to  mode,  which  can  be
       either a symbolic representation of changes to make, or an octal number
       representing the bit pattern for the new mode bits.

       The format of a symbolic mode is  [ugoa...][[+-=][perms...]...],  where
       perms  is  either zero or more letters from the set rwxXst, or a single
       letter from the set ugo.  Multiple symbolic modes can be  given,  sepa-
       rated by commas.

       A  combination  of the letters ugoa controls which users' access to the
       file will be changed: the user who owns it  (u),  other  users  in  the
       file's group (g), other users not in the file's group (o), or all users
       (a).  If none of these are given, the effect is as if a were given, but
       bits that are set in the umask are not affected.

       The  operator  +  causes the selected file mode bits to be added to the
       existing file mode bits of each file; - causes them to be removed;  and
       =  causes  them  to  be added and causes unmentioned bits to be removed
       except that a directory's unmentioned set user and group  ID  bits  are
       not affected.

       The  letters  rwxXst select file mode bits for the affected users: read
       (r), write (w), execute (or search for directories) (x), execute/search
       only  if  the file is a directory or already has execute permission for
       some user (X), set user or group ID on execution (s), restricted  dele-
       tion  flag or sticky bit (t).  Instead of one or more of these letters,
       you can specify exactly one of the letters ugo: the permissions granted
       to  the  user  who  owns the file (u), the permissions granted to other
       users who are members of the file's  group  (g),  and  the  permissions
       granted  to  users  that are in neither of the two preceding categories
       (o).

       A numeric mode is from one to  four  octal  digits  (0-7),  derived  by
       adding up the bits with values 4, 2, and 1.  Omitted digits are assumed
       to be leading zeros, except that if  the  first  digit  is  omitted,  a
       directory's  set  user  and  group ID bits are not affected.  The first
       digit selects the set user ID (4) and set group ID (2)  and  restricted
       deletion  or  sticky  (1) attributes.  The second digit selects permis-
       sions for the user who owns the file: read (4), write (2), and  execute
       (1); the third selects permissions for other users in the file's group,
       with the same values; and the fourth for other users not in the  file's
       group, with the same values.

       chmod never changes the permissions of symbolic links; the chmod system
       call cannot change their permissions.  This is not a problem since  the

OPTIONS

       Change the mode of each FILE to MODE.

       -c, --changes
              like verbose but report only when a change is made

       --no-preserve-root
              do not treat `/' specially (the default)

       --preserve-root
              fail to operate recursively on `/'

       -f, --silent, --quiet
              suppress most error messages

       -v, --verbose
              output a diagnostic for every file processed

       --reference=RFILE
              use RFILE's mode instead of MODE values

       -R, --recursive
              change files and directories recursively

       --help display this help and exit

       --version
              output version information and exit

       Each MODE is of the form `[ugoa]*([-+=]([rwxXst]*|[ugo]))+'.

AUTHOR

       Written by David MacKenzie and Jim Meyering.

REPORTING BUGS

       Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT

       Copyright (C) 2007 Free Software Foundation, Inc.
       This  is  free  software.   You may redistribute copies of it under the
       terms      of      the      GNU      General       Public       License
       <http://www.gnu.org/licenses/gpl.html>.   There  is NO WARRANTY, to the
       extent permitted by law.

SEE ALSO

       chmod(2)

       The full documentation for chmod is maintained as a Texinfo manual.  If
       the  info  and  chmod programs are properly installed at your site, the
       command