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