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.TH CHMOD 1 2020年三月 "GNU coreutils 8.32" 用戶命令
.SH 名稱
chmod \- 改變文件模式比特位
.SH 概述
\fBchmod\fP [\fI\,選項\/\fP]... \fI\,模式\/\fP[\fI\,,模式\/\fP]... \fI\,文件列表\/\fP...
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\fBchmod\fP [\fI\,選項\/\fP]... \fI\,八進制模式字符串 文件列表\/\fP...
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\fBchmod\fP [\fI\,選項\/\fP]... \fI\,\-\-reference=參考文件 文件列表\/\fP...
.SH 描述
本手冊頁記錄了 GNU 版本的 \fBchmod\fP。\fBchmod\fP 根據給定
\fI模式\fP改變每個給出文件的模式比特位，其模式字符串既可以是修改目標的符號表示，也可以是用一個八進制數字來代表新的模式比特位形式。
.PP
The format of a symbolic mode is
[\fBugoa\fP.\|.\|.][[\fB\-+=\fP][\fIperms\fP.\|.\|.].\|.\|.], where \fIperms\fP is either
zero or more letters from the set \fBrwxXst\fP, or a single letter from the set
\fBugo\fP.  Multiple symbolic modes can be given, separated by commas.
.PP
A combination of the letters \fBugoa\fP controls which users' access to the
file will be changed: the user who owns it (\fBu\fP), other users in the file's
group (\fBg\fP), other users not in the file's group (\fBo\fP), or all users
(\fBa\fP).  If none of these are given, the effect is as if (\fBa\fP) were given,
but bits that are set in the umask are not affected.
.PP
The operator \fB+\fP causes the selected file mode bits to be added to the
existing file mode bits of each file; \fB\-\fP causes them to be removed; and
\fB=\fP 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.
.PP
The letters \fBrwxXst\fP select file mode bits for the affected users: read
(\fBr\fP), write (\fBw\fP), execute (or search for directories)  (\fBx\fP),
execute/search only if the file is a directory or already has execute
permission for some user (\fBX\fP), set user or group ID on execution (\fBs\fP),
restricted deletion flag or sticky bit (\fBt\fP).  Instead of one or more of
these letters, you can specify exactly one of the letters \fBugo\fP: the
permissions granted to the user who owns the file (\fBu\fP), the permissions
granted to other users who are members of the file's group (\fBg\fP), and the
permissions granted to users that are in neither of the two preceding
categories (\fBo\fP).
.PP
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.
.PP
\fBchmod\fP never changes the permissions of symbolic links; the \fBchmod\fP
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, \fBchmod\fP changes the permissions
of the pointed\-to file.  In contrast, \fBchmod\fP ignores symbolic links
encountered during recursive directory traversals.
.SH "SETUID 和 SETGID 比特位"
\fBchmod\fP 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
\fIMODE\fP or \fIRFILE\fP to be ignored.  This behavior depends on the policy and
functionality of the underlying \fBchmod\fP system call.  When in doubt, check
the underlying system behavior.
.PP
For directories \fBchmod\fP 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 \fBu+s\fP and \fBg\-s\fP.  To clear these bits for directories
with a numeric mode requires an additional leading zero, or leading = like
\fB00755\fP , or \fB=755\fP
.SH "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 \fIrestricted deletion
flag\fP for the directory, and is commonly found on world\-writable directories
like \fB/tmp\fP.  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 \fIsticky bit\fP.
.SH 選項
.PP
將每個文件的權限模式變更至指定模式。使用 \fB\-\-reference\fP 選項時，把指定文件的模式設置爲與參考文件相同。
.TP 
\fB\-c\fP, \fB\-\-changes\fP
類似 verbose 選項，但只在做出修改時進行報告
.TP 
\fB\-f\fP, \fB\-\-silent\fP, \fB\-\-quiet\fP
隱藏大多數錯誤信息
.TP 
\fB\-v\fP, \fB\-\-verbose\fP
對每一個處理的文件輸出診斷信息
.TP 
\fB\-\-no\-preserve\-root\fP
不要對“/”特別對待（默認）
.TP 
\fB\-\-preserve\-root\fP
不要在“/”下進行遞歸操作
.TP 
\fB\-\-reference\fP=\fI\,參考文件\/\fP
使用參考文件的模式作爲具體模式值
.TP 
\fB\-R\fP, \fB\-\-recursive\fP
遞歸修改文件和目錄
.TP 
\fB\-\-help\fP
顯示此幫助信息並退出
.TP 
\fB\-\-version\fP
顯示版本信息並退出
.PP
每個模式字符串都應該匹配如下格式："[ugoa]*([\-+=]([rwxXst]*|[ugo]))+|[\-+=][0\-7]+"。
.SH 作者
由 David MacKenzie 和 Jim Meyering 編寫。
.SH 報告錯誤
GNU coreutils 的在線幫助： <https://www.gnu.org/software/coreutils/>
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請向 <https://translationproject.org/team/zh_CN.html> 報告翻譯錯誤。
.SH 版權
Copyright \(co 2020 Free Software Foundation, Inc.  License GPLv3+: GNU GPL
version 3 or later <https://gnu.org/licenses/gpl.html>.
.br
This is free software: you are free to change and redistribute it.  There is
NO WARRANTY, to the extent permitted by law.
.SH 參見
chmod(2)
.PP
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完整文檔請見： <https://www.gnu.org/software/coreutils/chmod>
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或者在本地使用： info \(aq(coreutils) chmod invocation\(aq
.SH "跋"
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本頁面中文版由中文 man 手冊頁計劃提供。
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中文 man 手冊頁計劃：\fBhttps://github.com/man-pages-zh/manpages-zh\fR