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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
?????? either 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
?????? except 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
?????? interpretation 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
?????? restricted? 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.

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

?????? --no-preserve-root
?? ?????? do not treat ‘/’ specially (the default)

?????? --preserve-root
?? ?????? fail to operate recursively on ‘/’

?????? -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 of the form ‘[ugoa]*([-+=]([rwxXst]*|[ugo]))+’.

AUTHOR
?????? Written by David MacKenzie and Jim Meyering.

REPORTING BUGS
?????? Report chmod bugs to bug-coreutils@gnu.org
?????? GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
?????? General help using GNU software: <http://www.gnu.org/gethelp/>
?????? Report chmod translation bugs to <http://translationproject.org/team/>

COPYRIGHT
?????? Copyright ? 2010 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 8.4?? ??? ??? June 2012?? ??? ??? ?????? CHMOD(1)

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