名稱

       chmod - 改變檔案模式位元位

概述

       chmod [選項]... 模式[,模式]... 檔案列表...
       chmod [選項]... 八進位制模式字串 檔案列表...
       chmod [選項]... --reference=參考檔案 檔案列表...

描述

       本手冊頁記錄了  GNU 版本的 chmod。chmod 根據給定 模式改變每個給出檔案的模式位元位，其模式字串既可以是修改
       目標的符號表示，也可以是用一個八進位制數字來代表新的模式位元位形式。

       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,
       separated 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 deletion 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  symbolic link listed on the command line, chmod changes the permissions of the pointed-to file.  In
       contrast, chmod ignores symbolic links encountered during recursive directory traversals.

SETUID 和 SETGID 位元位

       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  unless  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
       directories with a numeric mode requires an additional leading zero, or leading = like 00755 , or =755

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.

選項

       將每個檔案的許可權模式變更至指定模式。使用 --reference 選項時，把指定檔案的模式設定為與參考檔案相同。

       -c, --changes
              類似 verbose 選項，但只在做出修改時進行報告

       -f, --silent, --quiet
              隱藏大多數錯誤資訊

       -v, --verbose
              對每一個處理的檔案輸出診斷資訊

       --no-preserve-root
              不要對“/”特別對待（預設）

       --preserve-root
              不要在“/”下進行遞迴操作

       --reference=參考檔案
              使用參考檔案的模式作為具體模式值

       -R, --recursive
              遞迴修改檔案和目錄

       --help 顯示此幫助資訊並退出

       --version
              顯示版本資訊並退出

       每個模式字串都應該匹配如下格式："[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+"。

作者

       由 David MacKenzie 和 Jim Meyering 編寫。

報告錯誤

       GNU coreutils 的線上幫助： <https://www.gnu.org/software/coreutils/>
       請向 <https://translationproject.org/team/zh_CN.html> 報告翻譯錯誤。

版權

       Copyright  ©  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.

參見

       chmod(2)

       完整文件請見： <https://www.gnu.org/software/coreutils/chmod>
       或者在本地使用： info '(coreutils) chmod invocation'

跋

       本頁面中文版由中文 man 手冊頁計劃提供。
       中文 man 手冊頁計劃：https://github.com/man-pages-zh/manpages-zh

GNU coreutils 8.32                                 2020年三月                                           CHMOD(1)