Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
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.

       chmod preserves a directory's set-user-ID and set-group-ID bits	unless
       you  explicitly	specify	otherwise.  You	can set	or clear the bits with
       symbolic	modes like u+s and g-s,	and you	can set	(but  not  clear)  the
       bits with a numeric mode.

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]+'.

       GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Re-
       port chmod translation bugs to <http://translationproject.org/team/>

AUTHOR
       Written by David	MacKenzie and Jim Meyering.

COPYRIGHT
       Copyright  (C) 2013 Free	Software Foundation, Inc.  License GPLv3+: GNU
       GPL version 3 or	later <http://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)

       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 invocation'

       should give you access to the complete manual.

GNU coreutils 8.22		   June	2014			      CHMOD(1)

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

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=chmod&sektion=1&manpath=CentOS+7.1>

home | help