CHMOD linux command manual

CHMOD(1)                      User Commands                        CHMOD(1)

       chmod - change file access permissions

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

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

       The   format   of   a   symbolic   mode   is   '[ugoa...][[+-=][rwxXs-
       tugo...]...][,...]'.  Multiple symbolic operations 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 permissions selected to be  added  to  the
       existing  permissions of each file; '-' causes them to be removed; and
       '=' causes them to be the only permissions that the file has.

       The letters 'rwxXstugo' select the new permissions  for  the  affected
       users:  read  (r), write (w), execute (or access for directories) (x),
       execute only if the file is a directory or already has execute permis-
       sion  for some user (X), set user or group ID on execution (s), sticky
       (t), 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.  Any  omitted  digits  are
       assumed  to be leading zeros.  The first digit selects the set user ID
       (4) and set group ID (2) and sticky (1) attributes.  The second  digit
       selects  permissions  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  sys-
       tem call cannot change their permissions.  This is not a problem since
       the permissions of symbolic links are never used.  However,  for  each
       symbolic  link  listed  on the command line, chmod changes the permis-
       sions of the pointed-to file.  In  contrast,  chmod  ignores  symbolic
       links encountered during recursive directory traversals.

       On  older  Unix  systems, the sticky bit caused executable files to be
       hoarded in swap space.  This feature is not useful on modern  VM  sys-
       tems,  and  the  Linux  kernel ignores the sticky bit on files.  Other
       kernels may use the sticky bit on files for  system-defined  purposes.
       On some systems, only the superuser can set the sticky bit on files.

       When the sticky bit is set on a directory, files in that directory may
       be unlinked or renamed only by  root  or  their  owner.   Without  the
       sticky bit, anyone able to write to the directory can delete or rename
       files.  The sticky bit is commonly found on directories, such as /tmp,
       that are world-writable.

       Change the mode of each FILE to MODE.

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

              do not treat '/' specially (the default)

              fail to operate recursively on '/'

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

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

              use RFILE's mode instead of MODE values

       -R, --recursive
              change files and directories recursively

       --help display this help and exit

              output version information and exit

       Each  MODE  is one or more of the letters ugoa, one of the symbols +-=
       and one or more of the letters rwxXstugo.

       Written by David MacKenzie and Jim Meyering.

       Report bugs to .

       Copyright (C) 2004 Free Software Foundation, Inc.
       This is free software; see the source for copying  conditions.   There
       is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-

       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

              info coreutils chmod

       should give you access to the complete manual.

chmod (coreutils) 5.2.1            May 2004                          CHMOD(1)