📄 ch22_07.htm

📁 the unix power tools
💻 HTM
字号:
<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 22] 22.7 Using chmod to Change File Permission </TITLE><METANAME="DC.title"CONTENT="UNIX Power Tools"><METANAME="DC.creator"CONTENT="Jerry Peek, Tim O'Reilly &amp; Mike Loukides"><METANAME="DC.publisher"CONTENT="O'Reilly &amp; Associates, Inc."><METANAME="DC.date"CONTENT="1998-08-04T21:40:27Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-260-3"SCHEME="ISBN"><METANAME="DC.language"CONTENT="en-US"><METANAME="generator"CONTENT="Jade 1.1/O'Reilly DocBook 3.0 to HTML 4.0"><LINKREV="made"HREF="mailto:online-books@oreilly.com"TITLE="Online Books Comments"><LINKREL="up"HREF="ch22_01.htm"TITLE="22. File Security, Ownership, and Sharing"><LINKREL="prev"HREF="ch22_06.htm"TITLE="22.6 Protecting Files with the Sticky Bit "><LINKREL="next"HREF="ch22_08.htm"TITLE="22.8 The Handy chmod = Operator "></HEAD><BODYBGCOLOR="#FFFFFF"TEXT="#000000"><DIVCLASS="htmlnav"><H1><IMGSRC="gifs/smbanner.gif"ALT="UNIX Power Tools"USEMAP="#srchmap"BORDER="0"></H1><MAPNAME="srchmap"><AREASHAPE="RECT"COORDS="0,0,466,58"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="467,0,514,18"HREF="jobjects/fsearch.htm"ALT="Search this book"></MAP><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch22_06.htm"TITLE="22.6 Protecting Files with the Sticky Bit "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 22.6 Protecting Files with the Sticky Bit "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 22<BR>File Security, Ownership, and Sharing</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch22_08.htm"TITLE="22.8 The Handy chmod = Operator "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 22.8 The Handy chmod = Operator "BORDER="0"></A></TD></TR></TABLE>&nbsp;<HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-2991">22.7 Using chmod to Change File Permission </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-24067"></A><ACLASS="indexterm"NAME="AUTOID-24069"></A>To change a file's permissions, you need to use the <EMCLASS="emphasis">chmod</EM>command and you must be the file's owner or root.The command's syntax is pretty simple:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>chmod <CODECLASS="replaceable"><I>new-mode file(s)</I></CODE></B></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">The <CODECLASS="replaceable"><I>new-mode</I></CODE> describes the access permissions you want<EMCLASS="emphasis">after</EM> the change. There are twoways to specify the mode: you can use either a <EMCLASS="emphasis">numericmode</EM> or some symbols that describe the changes.I generally prefer the numeric mode (because I'm strange, Isuppose). Anyway, to usea numeric mode, decide what permissions youwant to have, <SPANCLASS="link">express them as an octal number (<ACLASS="linkend"HREF="ch01_23.htm"TITLE="File Access Permissions ">1.23</A>, <ACLASS="linkend"HREF="ch22_02.htm"TITLE="Tutorial on File and Directory Permissions ">22.2</A>)</SPAN>,and give a command like:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>chmod 644 report.txt</B></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">This gives read and write access to the owner of <EMCLASS="emphasis">report.txt</EM>and read-only access to everyone else.</P><PCLASS="para">Most users prefer to use the <EMCLASS="emphasis">symbolic mode</EM> to specify permissions.A symbolic <EMCLASS="emphasis">chmod</EM> command looks like this:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>chmod g-w report.txt</B></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">This means &quot;take away write access for group members.&quot;The symbols used in mode specifications are shown in <ACLASS="xref"HREF="ch22_07.htm#UPT-ART-2991-TAB-0"TITLE="chmod Symbolic Modes">Table 22.1</A>.&#13;</P><TABLECLASS="table"><CAPTIONCLASS="table"><ACLASS="title"NAME="UPT-ART-2991-TAB-0">Table 22.1: chmod Symbolic Modes</A></CAPTION><THEADCLASS="thead"><TRCLASS="row"VALIGN="TOP"><THCLASS="entry"ALIGN="LEFT"ROWSPAN="1"COLSPAN="1">Category</TH><THCLASS="entry"ALIGN="LEFT"ROWSPAN="1"COLSPAN="1"></TH><THCLASS="entry"ALIGN="LEFT"ROWSPAN="1"COLSPAN="1">Mode</TH><THCLASS="entry"ALIGN="LEFT"ROWSPAN="1"COLSPAN="1"></TH><THCLASS="entry"ALIGN="LEFT"ROWSPAN="1"COLSPAN="1">Description</TH></TR></THEAD><TBODYCLASS="tbody"><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Who:</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">u</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">User (owner) of the file.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">g</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Group members.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">o</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Others.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">a</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">All (i.e., user, group, and others).</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">What to do:</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">-</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Take away this permission. </TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">+</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Add the indicated permission.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">=</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"><SPANCLASS="link">Set exactly this permission (<ACLASS="linkend"HREF="ch22_08.htm"TITLE="The Handy chmod = Operator ">22.8</A>)</SPAN>.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Permissions:</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">r</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Read access.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">w</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Write access.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">x</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Execute access.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">X</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Give (or deny) execute permission to directories, or to filesthat have another &quot;execute&quot; bit set.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">s</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Set user or group ID (only valid with <CODECLASS="literal">+</CODE> or <CODECLASS="literal">-</CODE>).</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1"></TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">t</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">Set the<SPANCLASS="link">&quot;sticky bit&quot; (<ACLASS="linkend"HREF="ch22_06.htm"TITLE="Protecting Files with the Sticky Bit ">22.6</A>, <ACLASS="linkend"HREF="ch01_23.htm"TITLE="File Access Permissions ">1.23</A>)</SPAN>.</TD></TR></TBODY></TABLE><PCLASS="para">(Article<ACLASS="xref"HREF="ch22_02.htm"TITLE="Tutorial on File and Directory Permissions ">22.2</A>explains the &quot;Who&quot; and &quot;Permissions&quot; categories.)Here are a few example symbolic modes:&#13;</P><DLCLASS="variablelist"><DTCLASS="term"><CODECLASS="literal">o=r</CODE></DT><DDCLASS="listitem"><PCLASS="para">Set others access to read-only, regardless of what other bits are set.</P></DD><DTCLASS="term"><CODECLASS="literal">o+r</CODE></DT><DDCLASS="listitem"><PCLASS="para">Add read access for others.</P></DD><DTCLASS="term"><CODECLASS="literal">go-w</CODE></DT><DDCLASS="listitem"><PCLASS="para">Take away write access for group members and others.</P></DD><DTCLASS="term"><CODECLASS="literal">a=rw</CODE></DT><DDCLASS="listitem"><PCLASS="para">Give everyone (user, group, and others) read-write (but not execute) access.&#13;</P></DD></DL><PCLASS="para">Remember that <CODECLASS="literal">+</CODE> and <CODECLASS="literal">-</CODE> add or delete certain permissions, butleave the others untouched. The commands below show how permissionsare added and subtracted:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>ls -l foo</B></CODE>-rwx---x  1 mikel           0 Mar 30 11:02 foo% <CODECLASS="userinput"><B>chmod a+x foo</B></CODE>% <CODECLASS="userinput"><B>ls -l foo</B></CODE>-rwx-x-x  1 mikel           0 Mar 30 11:02 foo% <CODECLASS="userinput"><B>chmod o-x,g+r foo</B></CODE>% <CODECLASS="userinput"><B>ls -l foo</B></CODE>-rwxr-x--  1 mikel           0 Mar 30 11:02 foo%</PRE></BLOCKQUOTE></P><PCLASS="para">Note the last <EMCLASS="emphasis">chmod</EM> command. It shows something we haven'tmentioned before. With symbolic mode, you're allowed to combine two(or more) specifications, separated by commas. This command says&quot;take away execute permission for others, and add read access forgroup members.&quot;</P><TABLECLASS="para.programreference"BORDER="1"><TR><THVALIGN="TOP"><ACLASS="programreference"HREF="examples/index.htm"TITLE="chmod">chmod</A><BR></TH><TDVALIGN="TOP">&#13;The GNU version of <EMCLASS="emphasis">chmod</EM> is on the CD-ROM.</TD></TR></TABLE><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-24227"></A><ACLASS="indexterm"NAME="AUTOID-24230"></A><ACLASS="indexterm"NAME="AUTOID-24233"></A>On occasion, I've wanted to change the permissions of a wholedirectory tree: all the files in a directory and all of itssubdirectories. In this case, you want to use <EMCLASS="emphasis">chmod -R</EM> (the <EMCLASS="emphasis">R</EM>stands for recursive) or<SPANCLASS="link"><EMCLASS="emphasis">find -exec</EM> (<ACLASS="linkend"HREF="ch17_10.htm"TITLE="Running Commands on What You Find ">17.10</A>)</SPAN>.You won't need this often, but when you do,it's a real lifesaver.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">ML</SPAN></P></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch22_06.htm"TITLE="22.6 Protecting Files with the Sticky Bit "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 22.6 Protecting Files with the Sticky Bit "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="book"HREF="index.htm"TITLE="UNIX Power Tools"><IMGSRC="gifs/txthome.gif"SRC="gifs/txthome.gif"ALT="UNIX Power Tools"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch22_08.htm"TITLE="22.8 The Handy chmod = Operator "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 22.8 The Handy chmod = Operator "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">22.6 Protecting Files with the Sticky Bit </TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="index"HREF="index/idx_0.htm"TITLE="Book Index"><IMGSRC="gifs/index.gif"SRC="gifs/index.gif"ALT="Book Index"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172">22.8 The Handy chmod = Operator </TD></TR></TABLE><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><IMGSRC="gifs/smnavbar.gif"SRC="gifs/smnavbar.gif"USEMAP="#map"BORDER="0"ALT="The UNIX CD Bookshelf Navigation"><MAPNAME="map"><AREASHAPE="RECT"COORDS="0,0,73,21"HREF="../index.htm"ALT="The UNIX CD Bookshelf"><AREASHAPE="RECT"COORDS="74,0,163,21"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="164,0,257,21"HREF="../unixnut/index.htm"ALT="UNIX in a Nutshell"><AREASHAPE="RECT"COORDS="258,0,321,21"HREF="../vi/index.htm"ALT="Learning the vi Editor"><AREASHAPE="RECT"COORDS="322,0,378,21"HREF="../sedawk/index.htm"ALT="sed &amp; awk"><AREASHAPE="RECT"COORDS="379,0,438,21"HREF="../ksh/index.htm"ALT="Learning the Korn Shell"><AREASHAPE="RECT"COORDS="439,0,514,21"HREF="../lrnunix/index.htm"ALT="Learning the UNIX Operating System"></MAP></DIV></BODY></HTML>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -