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CHMOD(1) User Commands CHMOD(1)
NAME
chmod - change file mode bitsSYNOPSIS
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 exitEach 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
commandinfo coreutils 'chmod invocation'
should give you access to the complete manual.
GNU coreutils 8.4 May 2016 CHMOD(1)
CHOWN(1) User Commands CHOWN(1)
NAME
chown - change file owner and groupSYNOPSIS
chown [OPTION]... [OWNER][:[GROUP]] FILE...
chown [OPTION]... --reference=RFILE FILE...DESCRIPTION
This manual page documents the GNU version of chown. chown changes the
user and/or group ownership of each given file. If only an owner (a
user name or numeric user ID) is given, that user is made the owner of
each given file, and the files’ group is not changed. If the owner is
followed by a colon and a group name (or numeric group ID), with no
spaces between them, the group ownership of the files is changed as
well. If a colon but no group name follows the user name, that user is
made the owner of the files and the group of the files is changed to
that user’s login group. If the colon and group are given, but the
owner is omitted, only the group of the files is changed; in this case,
chown performs the same function as chgrp. If only a colon is given,
or if the entire operand is empty, neither the owner nor the group is
changed.OPTIONS
Change the owner and/or group of each FILE to OWNER and/or GROUP. With
--reference, change the owner and group of each FILE to those of RFILE.-c, --changes
like verbose but report only when a change is made--dereference
affect the referent of each symbolic link (this is the default),
rather than the symbolic link itself-h, --no-dereference
affect each symbolic link instead of any referenced file (useful
only on systems that can change the ownership of a symlink)--from=CURRENT_OWNER:CURRENT_GROUP
change the owner and/or group of each file only if its current
owner and/or group match those specified here. Either may be
omitted, in which case a match is not required for the omitted
attribute.--no-preserve-root
do not treat ‘/’ specially (the default)--preserve-root
fail to operate recursively on ‘/’-f, --silent, --quiet
suppress most error messages--reference=RFILE
use RFILE’s owner and group rather than specifying OWNER:GROUP
values-R, --recursive
operate on files and directories recursively-v, --verbose
output a diagnostic for every file processedThe following options modify how a hierarchy is traversed when the -R
option is also specified. If more than one is specified, only the
final one takes effect.-H if a command line argument is a symbolic link to a directory,
traverse it-L traverse every symbolic link to a directory encountered
-P do not traverse any symbolic links (default)
--help display this help and exit
--version
output version information and exitOwner is unchanged if missing. Group is unchanged if missing, but
changed to login group if implied by a ‘:’ following a symbolic OWNER.
OWNER and GROUP may be numeric as well as symbolic.EXAMPLES
chown root /u
Change the owner of /u to "root".chown root:staff /u
Likewise, but also change its group to "staff".chown -hR root /u
Change the owner of /u and subfiles to "root".AUTHOR
Written by David MacKenzie and Jim Meyering.REPORTING BUGS
Report chown 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 chown 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
chown(2)The full documentation for chown is maintained as a Texinfo manual. If
the info and chown programs are properly installed at your site, the
commandinfo coreutils 'chown invocation'
should give you access to the complete manual.
GNU coreutils 8.4 May 2016 CHOWN(1)
[oh@localhost 桌面]$
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