redhat man page for chmod

CHMOD(1)								FSF								  CHMOD(1)

NAME
       chmod - change file access permissions

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 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  com-
       mas.

       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 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 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 permis-
       sions of the pointed-to file.  In contrast, chmod ignores symbolic links encountered during recursive directory traversals.

STICKY FILES
       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.

STICKY DIRECTORIES
       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.

OPTIONS
       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
       Written by David MacKenzie.

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

COPYRIGHT
       Copyright (C) 2002 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-
       LAR PURPOSE.

SEE ALSO
       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 (coreutils) 4.5.3 					   February 2003							  CHMOD(1)