index00.sgml

Shall高级编程

         </para></listitem>
       <listitem><para><link linkend="csws">Word splitting</link></para></listitem>
         </itemizedlist></para>

      <para><link linkend="commenth">Comment headers</link>,
        special purpose</para>

      <para>Commenting out blocks of code
        <itemizedlist>
      <listitem><para>Using an <link
        linkend="cblock1"><firstterm>anonymous</firstterm> here
        document</link></para></listitem>
      <listitem><para>Using an <link linkend="comoutbl">
        <firstterm>if-then</firstterm> construct</link></para></listitem>
         </itemizedlist></para>



      <para><link linkend="ccomparison1">Compound comparison</link>
         operators</para>

<!-- ************************************************************ -->
      <para><link linkend="facompression1">Compression utilities</link>
         <itemizedlist>
      <listitem><para><link linkend="bzipref">bzip2</link></para></listitem>
      <listitem><para><link
        linkend="compressref">compress</link></para></listitem>
      <listitem><para><link linkend="gzipref">gzip</link></para></listitem>
      <listitem><para><link linkend="zipref">zip</link></para></listitem>
         </itemizedlist></para>
<!-- ************************************************************ -->
      <para><link linkend="brkcont1">continue</link> loop control command</para>

<!-- ***************************************************************** -->
      <para><link linkend="controlcharref">Control characters</link>
         <itemizedlist>
      <listitem><para><link linkend="ctlcref">Control-C</link>,
         <firstterm>break</firstterm></para></listitem>
      <listitem><para><link linkend="ctldref">Control-D</link>,
         terminate / log out / erase</para></listitem>
      <listitem><para><link linkend="ctlgref">Control-G</link>,
         <userinput>BEL</userinput>
         (<firstterm>beep</firstterm>)</para></listitem>
      <listitem><para><link linkend="ctlhref">Control-H</link>,
         <firstterm>rubout</firstterm></para></listitem>
      <listitem><para><link linkend="ctljref">Control-J</link>,
         <firstterm>newline</firstterm></para></listitem>
      <listitem><para><link linkend="ctlmref">Control-M</link>,
         carriage return</para></listitem>
         </itemizedlist></para>
<!-- ***************************************************************** -->

      <para><link linkend="cronref">cron</link>, scheduling
        <firstterm>daemon</firstterm></para>
      <para><link linkend="cstyle"><firstterm>C</firstterm>-style syntax
        </link>, for handling variables</para>

      <para>Curly brackets {}
           <itemizedlist>
      <listitem><para><link linkend="curlybracketsref">in
         <firstterm>find</firstterm> command</link></para></listitem>
      <listitem><para><link linkend="escpcb">in an
         <firstterm>Extended Regular
	 Expression</firstterm></link></para></listitem>
      <listitem><para><link linkend="xargscurlyref">in
         <firstterm>xargs</firstterm></link></para></listitem>
           </itemizedlist></para>

      <para>* * *</para>

      <para><link linkend="daemonref">Daemons</link>, in UNIX-type OS</para>

      <para><link linkend="dateref">date</link></para>
      <para><link linkend="dcref">dc</link>, calculator utility</para>

      <para><link linkend="ddref">dd</link>, <firstterm>data
        duplicator</firstterm> command
	  <itemizedlist>

      <listitem><para><link
        linkend="ddconversions">Conversions</link></para></listitem>
      <listitem><para><link linkend="ddcopy">Copying raw data</link>
        to/from devices</para></listitem>
      <listitem><para><link
        linkend="ddfdel">File deletion</link>,
        <firstterm>secure</firstterm></para></listitem>
      <listitem><para><link
        linkend="ddkeystrokes">Keystrokes</link>, capturing</para></listitem>
      <listitem><para><link
        linkend="ddoptions">Options</link></para></listitem>
      <listitem><para><link
        linkend="ddrandom">Random access</link> on a data
        stream</para></listitem>
      <listitem><para><link
        linkend="ddswap">Swapfiles</link>, initializing</para></listitem>
      <listitem><para><link linkend="ddlink">Thread on
        <firstterm>www.linuxquestions.org</firstterm></link></para></listitem>

	  </itemizedlist></para>

      <para><link linkend="debugging">Debugging scripts</link>
         <itemizedlist>
      <listitem><para><link
        linkend="debugtools">Tools</link></para></listitem>
      <listitem><para><link
        linkend="debugtrap"><firstterm>Trapping</firstterm> at
        exit</link></para></listitem>
      <listitem><para><link
        linkend="trapref1"><firstterm>Trapping</firstterm>
          signals</link></para></listitem>
         </itemizedlist></para>

      <para><link linkend="numconstants">Decimal number</link>,
         Bash interprets numbers as</para>

      <para><link linkend="declare1ref">declare</link> builtin</para>
         <itemizedlist>
      <listitem><para><link
        linkend="declareopsref1">options</link></para></listitem>
         </itemizedlist>

      <para><link linkend="defparam">Default parameters</link></para>

<!-- ******************************************************************* -->
      <para><link linkend="devprocref"><filename
         class="directory">/dev</filename></link> directory

         <itemizedlist>
      <listitem><para><link
         linkend="devnullref"><filename>/dev/null</filename></link>
           pseudo-device file</para></listitem>

      <listitem><para><link
         linkend="urandomref"><filename>/dev/urandom</filename></link>
         pseudo-device file, generating pseudorandom numbers
         with</para></listitem>

      <listitem><para><link
         linkend="zerosref1"><filename>/dev/zero</filename></link>,
         pseudo-device file</para></listitem>
         </itemizedlist></para>
<!-- ******************************************************************* -->


      <para><link linkend="dialogref"><firstterm>dialog</firstterm></link>,
         utility for generating <firstterm>dialog</firstterm> boxes in
         a script</para>
      <para><link linkend="dirstackref"><varname>$DIRSTACK</varname></link>
         <firstterm>directory stack</firstterm></para>
      <para><link linkend="disabledcommref">Disabled commands</link>,
         in <firstterm>restricted shells</firstterm></para>
      <para><link linkend="doinref">do</link> keyword,
         begins execution of commands within a <link
	 linkend="loopref00">loop</link></para>
      <para><link linkend="doinref">done</link> keyword,
         terminates a loop</para>
      <para><link linkend="dosbatch1"><firstterm>DOS</firstterm> batch
         files</link>, converting to shell scripts</para>
      <para><link linkend="dosunixequiv"><firstterm>DOS</firstterm>
        commands</link>, UNIX equivalents of
        (<command>table</command>)</para>
      <para><link linkend="dotfilesref"><firstterm>dot files</firstterm></link>,
         <quote>hidden</quote> setup and configuration files</para>
      <para><link linkend="dblbrackets">Double brackets</link>
         <command>[[ ... ]]</command> <link linkend="ifthen">test</link>
         construct</para>
      <para><link linkend="dblquo">Double quotes</link>
      <command>" ... "</command> <firstterm>weak</firstterm> quoting</para>
      <para><link linkend="doublespace">Double-spacing a text
        file</link>, using <link linkend="sedref">sed</link></para>

      <para>* * *</para>

      <para><command>-e </command>
        <link linkend="rtif">File exists</link> test</para>

      <para><link linkend="echoref">echo</link>
         <itemizedlist>
      <listitem><para><link linkend="echogrepref">Feeding commands down
        a <firstterm>pipe</firstterm></link></para></listitem>
      <listitem><para><link linkend="echocs">Setting a variable</link>
        using <link linkend="commandsubref">command
        substitution</link></para></listitem>
      <listitem><para><link
        linkend="binecho"><filename>/bin/echo</filename></link>,
	external <firstterm>echo</firstterm> command</para></listitem>
         </itemizedlist></para>

      <para><link linkend="elifref1"><command>elif</command></link>, Contraction
         of <firstterm>else</firstterm> and <firstterm>if</firstterm></para>
      <para><link linkend="caseesac1">esac</link>, keyword terminating
        <firstterm>case</firstterm> construct</para>
      <para><link linkend="envref"><firstterm>Environmental</firstterm>
         variables</link></para>
      <para><link linkend="equalref"> -eq </link>,
         <firstterm>is-equal-to</firstterm> <link linkend="icomparison1">integer
	 comparison</link> test</para>
       <para><link linkend="primes0">Eratosthenes,
         Sieve of</link>, algorithm for generating prime numbers</para>
      <para><link linkend="spm">Escaped characters</link>,
         special meanings of</para>
      <para><link linkend="euidref"><varname>$EUID</varname></link>,
         <firstterm>Effective user ID</firstterm></para>

      <para><link linkend="evalref">eval</link>,
         Combine and <firstterm>evaluate</firstterm> expression(s),
	 with variable expansion
	 <itemizedlist>
      <listitem><para><link linkend="evaleff">Effects
        of</link>, <firstterm>Example script</firstterm></para></listitem>
      <listitem><para><link linkend="evalforced">Forces
        <firstterm>reevaluation</firstterm></link> of
	arguments</para></listitem>
      <listitem><para><link linkend="evalrisk">Risk of
        using</link></para></listitem>
	 </itemizedlist></para>

      <para><link linkend="usingexecref">exec</link> command,
         using in <link linkend="ioredirref">redirection</link></para>

      <para><link linkend="exercises">Exercises</link></para>

<!-- ********************** -->
      <para>Exit and Exit status
        <itemizedlist>
      <listitem><para><link linkend="exitcommandref">exit</link>
         command</para></listitem>

      <listitem>
        <para><link linkend="exitstatusref">Exit status</link>
	  (<firstterm>exit code</firstterm>, <firstterm>return</firstterm>
	  status of a command)</para>
        <para><link linkend="exitcodesref"><command>Table</command></link>,
	  <firstterm>Exit
          codes</firstterm> with special meanings</para>
        <para><link linkend="excoor">Out of range</link></para>
         <para><link linkend="exitreturn1">
           Specified by a <firstterm>function
           return</firstterm></link></para>
         <para><link
           linkend="exitsuccess"><firstterm>Successful</firstterm></link>,
	   <command>0</command></para>
      </listitem>

        </itemizedlist></para>
<!-- ********************** -->

      <para><link linkend="exportref2">Export</link>,
         to make available variables to <link
         linkend="childref">child processes</link>
	 <itemizedlist>
      <listitem><para><link linkend="exportawk">Passing a variable
        to an embedded <firstterm>awk</firstterm>
	script</link></para></listitem>
	 </itemizedlist></para>

<!-- ********************** -->
      <para><link linkend="exprref">expr</link>,
         <firstterm>Expression</firstterm> evaluator
	   <itemizedlist>
      <listitem><para><link linkend="expextrsub">Substring
         extraction</link></para></listitem>
      <listitem><para><link linkend="substringindex2">Substring
         <firstterm>index</firstterm> (numerical position in
         string)</link></para></listitem>
      <listitem><para><link linkend="exprmatch">Substring
         matching</link></para></listitem>
	   </itemizedlist></para>
<!-- ********************** -->

      <para><link linkend="extregex">Extended <firstterm>Regular
         Expressions</firstterm></link>
	  <itemizedlist>
      <listitem><para><command>? </command> (question mark)
          <link linkend="quexregex">Match zero / one characters</link>
	  </para></listitem>
        <listitem><para><command>( ... ) </command>
          <link linkend="parengrps">Group
	  of expressions</link></para></listitem>
        <listitem><para><command>\{ N \}</command>
         <link linkend="escpcb"><quote>Curly</quote> brackets</link>,
         <firstterm>escaped</firstterm>,
	 number of character sets to match</para></listitem>
      <listitem><para><command>+ </command>
          <link linkend="plusref"><firstterm>Character
          match</firstterm></link></para></listitem>
	  </itemizedlist></para>

      <para>* * *</para>

      <para><link linkend="falseref">false</link>,
        returns <firstterm>unsuccessful</firstterm> (1) <link
        linkend="exitstatusref">exit status</link></para>
      <para><link linkend="fdref">File descriptors</link></para>
         <itemizedlist>
      <listitem><para><link linkend="cfd">Closing</link></para>

        <para><command>n&lt;&amp;-</command>
           Close input file descriptor <firstterm>n</firstterm></para>
        <para><command>0&lt;&amp;-</command>,
	   <command>&lt;&amp;-</command>
           Close <filename>stdin</filename></para>

        <para><command>n&gt;&amp;-</command>
          Close output file descriptor <firstterm>n</firstterm></para>
        <para><command>1&gt;&amp;-</command>,
	   <command>&gt;&amp;-</command>
	   Close <filename>stdout</filename></para>

      </listitem>

      <listitem><para><link linkend="fdref1">File handles in
        <firstterm>C</firstterm></link>, similarity to</para></listitem>

         </itemizedlist>

      <para><link linkend="findref">find</link>
         <itemizedlist>
      <listitem><para><command>{} </command>
        <link linkend="curlybracketsref">Curly
        brackets</link></para></listitem>
      <listitem><para><command>\; </command>
        <link linkend="findref0"><firstterm>Escaped</firstterm>
        semicolon</link></para></listitem>
	 </itemizedlist></para>

      <para><link linkend="filterdef">Filter</link>
         <itemizedlist>
      <listitem><para><link linkend="filterdash">Using <token>-</token>
        with file-processing utility as a filter</link></para></listitem>
      <listitem><para><link linkend="filteroutp">
         Feeding output of a filter back to <emphasis>same</emphasis>
	 filter</link></para></listitem>
	 </itemizedlist></para>

      <para><link linkend="nofloatingpoint">Floating point numbers</link>,