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CHMOD(1)

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NAME    [Toc]    [Back]

       chmod - change file access permissions

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

       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 number representing
 the bit pattern for the new permissions.

       The   format   of   a   symbolic   mode	 is    `[ugoa...][[+-=][rwxXstugo...]...][,...]'.
   Multiple symbolic operations can be given, separated
 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  permission
  for  some user (X), set user or group ID on execution (s), sticky
       (t), the permissions that the user who owns the file currently has  for
       it  (u),  the permissions that other users in the file's group have for
       it (g), and the permissions that other users not in  the  file's  group
       have for it (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 system
       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 permissions of
       the pointed-to file.  In contrast, chmod ignores symbolic links encountered
 during recursive directory traversals.

STICKY FILES    [Toc]    [Back]

       On  older  Unix	systems,  the sticky bit caused executable files to be
       hoarded in swap space.  This feature is not useful on  modern  VM  systems,
 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.

STICKY DIRECTORIES    [Toc]    [Back]

       When  the sticky bit is set on a directory, files in that directory may
       only be unlinked or renamed 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,
       which are world-writable.

OPTIONS    [Toc]    [Back]

       Change the mode of each FILE to MODE.

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

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

AUTHOR    [Toc]    [Back]

       Written by David MacKenzie.

REPORTING BUGS    [Toc]    [Back]

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

COPYRIGHT    [Toc]    [Back]

       Copyright (C) 2001 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 PARTICULAR
       PURPOSE.

SEE ALSO    [Toc]    [Back]

      
      
       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 chmod

       should give you access to the complete manual.



chmod (fileutils) 4.1		  March 2002			      CHMOD(1)
[ Back ]
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