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CHMOD(1)			 User Commands			      CHMOD(1)

NAME
       chmod - change file mode	bits

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  ei-
       ther  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 ex-
       cept 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.  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 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 sym-
       bolic link listed on the	command	line, chmod changes the	permissions of
       the pointed-to file.  In	contrast, chmod	ignores	symbolic links encoun-
       tered during recursive directory	traversals.

SETUID AND SETGID BITS
       chmod clears the	set-group-ID bit of a regular file if the file's group
       ID  does	 not  match the	user's effective group ID or one of the	user's
       supplementary group IDs,	unless the user	 has  appropriate  privileges.
       Additional restrictions may cause the set-user-ID and set-group-ID bits
       of MODE or RFILE	to be ignored.	This behavior depends  on  the	policy
       and  functionality of the underlying chmod system call.	When in	doubt,
       check the underlying system behavior.

       For directories chmod preserves set-user-ID and set-group-ID  bits  un-
       less  you  explicitly specify otherwise.	 You can set or	clear the bits
       with symbolic modes like	u+s and	g-s.  To clear these bits for directo-
       ries  with a numeric mode requires an additional	leading	zero, or lead-
       ing = like 00755	, or =755

RESTRICTED DELETION FLAG OR STICKY BIT
       The restricted deletion flag or sticky bit is a single bit,  whose  in-
       terpretation  depends  on  the file type.  For directories, it prevents
       unprivileged users from removing	or renaming a file  in	the  directory
       unless  they  own  the  file  or	 the directory;	this is	called the re-
       stricted	deletion flag for the directory,  and  is  commonly  found  on
       world-writable  directories like	/tmp.  For regular files on some older
       systems,	the bit	saves the program's text image on the swap  device  so
       it will load more quickly when run; this	is called the sticky bit.

OPTIONS
       Change  the  mode  of  each FILE	to MODE.  With --reference, change the
       mode of each FILE to that of RFILE.

       -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

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

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

       --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]))+|[-+=][0-7]+'.

AUTHOR
       Written by David	MacKenzie and Jim Meyering.

REPORTING BUGS
       GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
       Report any translation bugs to <https://translationproject.org/team/>

COPYRIGHT
       Copyright  (C) 2020 Free	Software Foundation, Inc.  License GPLv3+: GNU
       GPL version 3 or	later <https://gnu.org/licenses/gpl.html>.
       This is free software: you are free  to	change	and  redistribute  it.
       There is	NO WARRANTY, to	the extent permitted by	law.

SEE ALSO
       chmod(2)

       Full documentation <https://www.gnu.org/software/coreutils/chmod>
       or available locally via: info '(coreutils) chmod invocation'

GNU coreutils 8.32		  March	2020			      CHMOD(1)

NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO

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