Linux命令:chown

Linux命令:chmod

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chmod --help

 1 Usage: chmod [OPTION]... MODE[,MODE]... FILE...
 2   or:  chmod [OPTION]... OCTAL-MODE FILE...
 3   or:  chmod [OPTION]... --reference=RFILE FILE...
 4 Change the mode of each FILE to MODE.
 5 With --reference, change the mode of each FILE to that of RFILE.
 6 
 7   -c, --changes          like verbose but report only when a change is made
 8   -f, --silent, --quiet  suppress most error messages
 9   -v, --verbose          output a diagnostic for every file processed
10       --no-preserve-root  do not treat '/' specially (the default)
11       --preserve-root    fail to operate recursively on '/'
12       --reference=RFILE  use RFILE's mode instead of MODE values
13   -R, --recursive        change files and directories recursively
14       --help     display this help and exit
15       --version  output version information and exit
16 
17 Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.
18 
19 GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
20 For complete documentation, run: info coreutils 'chmod invocation'

man chmod

  1 CHMOD(1)                                                                            User Commands                                                                            CHMOD(1)
  2 
  3 
  4 
  5 NAME
  6        chmod - change file mode bits
  7 
  8 SYNOPSIS
  9        chmod [OPTION]... MODE[,MODE]... FILE...
 10        chmod [OPTION]... OCTAL-MODE FILE...
 11        chmod [OPTION]... --reference=RFILE FILE...
 12 
 13 DESCRIPTION
 14        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
 15        changes to make, or an octal number representing the bit pattern for the new mode bits.
 16 
 17        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
 18        symbolic modes can be given, separated by commas.
 19 
 20        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
 21        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.
 22 
 23        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
 24        causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected.
 25 
 26        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
 27        or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t).  Instead of one or more of these  let‐
 28        ters, 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
 29        file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o).
 30 
 31        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
 32        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:
 33        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
 34        file's group, with the same values.
 35 
 36        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
 37        are never used.  However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file.  In contrast, chmod ignores symbolic  links
 38        encountered during recursive directory traversals.
 39 
 40 SETUID AND SETGID BITS
 41        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
 42        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
 43        policy and functionality of the underlying chmod system call.  When in doubt, check the underlying system behavior.
 44 
 45        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,
 46        and you can set (but not clear) the bits with a numeric mode.
 47 
 48 RESTRICTED DELETION FLAG OR STICKY BIT
 49        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
 50        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-
 51        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;
 52        this is called the sticky bit.
 53 
 54 OPTIONS
 55        Change the mode of each FILE to MODE.  With --reference, change the mode of each FILE to that of RFILE.
 56 
 57        -c, --changes
 58               like verbose but report only when a change is made
 59 
 60        -f, --silent, --quiet
 61               suppress most error messages
 62 
 63        -v, --verbose
 64               output a diagnostic for every file processed
 65 
 66        --no-preserve-root
 67               do not treat '/' specially (the default)
 68 
 69        --preserve-root
 70               fail to operate recursively on '/'
 71 
 72        --reference=RFILE
 73               use RFILE's mode instead of MODE values
 74 
 75        -R, --recursive
 76               change files and directories recursively
 77 
 78        --help display this help and exit
 79 
 80        --version
 81               output version information and exit
 82 
 83        Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.
 84 
 85        GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report chmod translation bugs to <http://translationproject.org/team/>
 86 
 87 AUTHOR
 88        Written by David MacKenzie and Jim Meyering.
 89 
 90 COPYRIGHT
 91        Copyright © 2013 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
 92        This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.
 93 
 94 SEE ALSO
 95        chmod(2)
 96 
 97        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
 98 
 99               info coreutils 'chmod invocation'
100 
101        should give you access to the complete manual.
102 
103 
104 
105 GNU coreutils 8.22                                                                   October 2018                                                                            CHMOD(1)

posted on 2019-03-25 21:24 国民时代阅读(148) 评论(0) 编辑收藏举报

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