index00.sgml

Shall高级编程

      <para>This index / glossary / quick-reference lists many of the
	important topics covered in the text. Terms are arranged
	in <emphasis>approximate</emphasis> ASCII sorting order,
	<emphasis>reshuffled as necessary</emphasis> for enhanced
	clarity.</para>

      <para>Note that <emphasis>commands</emphasis> are indexed
	in <link linkend="part4A">Part 4</link>.</para>

      <para>* * *</para>

<!-- Characters and symbols -->
      <para><command>^ </command> (caret)
         <link linkend="beglineref">Beginning-of-line</link>, in a <link
         linkend="regexref">Regular Expression</link></para>


      <para><command>~ </command> <firstterm>Tilde</firstterm>
         <itemizedlist>

	 <listitem><para>
	 <command>~ </command>
         <link linkend="tilderef">home directory</link>, corresponds
           to <link
           linkend="homedirref"><varname>$HOME</varname></link>
          </para></listitem>

<!-- ********************** -->

	 <listitem><para>
            <command>~/ </command>
	 <link linkend="tilderef"> <firstterm>Current user's</firstterm>
	   home directory</link>
          </para></listitem>

	 <listitem><para>
            <command>~+ </command>
         <link linkend="workingdirref"><emphasis>Current</emphasis>
         working directory</link>
          </para></listitem>

	 <listitem><para>
            <command>~- </command>
         <link linkend="prevworkingdir"><emphasis>Previous</emphasis>
         working directory</link>
          </para></listitem>

         </itemizedlist>
	 </para>

<!-- ********************** -->

      <para><command>= </command> <firstterm>Equals</firstterm> sign
         <itemizedlist>

	 <listitem><para>
            <command>= </command>
         <link linkend="eqref">Variable assignment</link> operator
          </para></listitem>

	 <listitem><para>
            <command>= </command>
         <link linkend="scomparison1">String comparison</link> operator
          </para>
	 <para>
            <command>== </command>
        <link linkend="scomparison2">String comparison</link> operator
          </para></listitem>

	 <listitem>
	   <para>
            <command>=~ </command>
            <firstterm>Regular Expression</firstterm>
	    <link linkend="regexmatchref">match</link> operator
          </para>
	   <para><link linkend="findsplit0"><firstterm>Example
	     script</firstterm></link></para>
	  </listitem>

         </itemizedlist>
	 </para>


<!-- ********************** -->


      <para><command>&lt; </command> Left angle bracket
         <itemizedlist>

	 <listitem><para>Is-less-than</para>
         <para><link linkend="ltref">String comparison</link></para>
	 <para>
         <link linkend="intlt">Integer comparison</link> within
	 <link linkend="dblparens">double parentheses</link>
          </para></listitem>


	 <listitem><para>Redirection</para>

	 <para>
            <command>&lt; </command>
         <link linkend="ioredirectionref2"><filename>stdin</filename></link>
          </para>
	 <para>
            <command>&lt;&lt; </command>
         <link linkend="heredocrrref"><firstterm>Here document</firstterm></link>
          </para>
	 <para>
            <command>&lt;&lt;&lt; </command>
         <link linkend="herestringref"><firstterm>Here string</firstterm></link>
          </para>
	 <para>
            <command>&lt;&gt; </command>
         <link linkend="redirrw">Opening a file</link> for
         <emphasis>both</emphasis> reading and writing
          </para></listitem>

         </itemizedlist>
	 </para>

<!-- ********************** -->

      <para><command>&gt; </command> Right angle bracket
         <itemizedlist>

	 <listitem><para>Is-greater-than</para>
         <para><link linkend="gtref">String comparison</link></para>
	 <para><link linkend="intgt">Integer comparison</link>,
            within <firstterm>double parentheses</firstterm>
          </para></listitem>

<!-- *** -->
	 <listitem><para>Redirection</para>

        <para><command>&gt; </command>
         <link linkend="ioredirectionref">Redirect
         <filename>stdout</filename></link> to a file
          </para>
	 <para>
            <command>&gt;&gt; </command>
         <link linkend="ioredirectionref">Redirect
         <filename>stdout</filename></link> to a file,
         but <firstterm>append</firstterm>
          </para>

	 <para><command>i&gt;&amp;j </command>
            <link linkend="ioredirectionref1">Redirect
	    <firstterm>file descriptor</firstterm>
	    <filename>i</filename></link> to
	    <firstterm>file descriptor</firstterm>
	    <filename>j</filename></para>
	 <para>
            <command>&gt;&amp;j </command>
            <link linkend="ioredirectionref1">Redirect
	    <filename>stdout</filename></link> to
	    <firstterm>file descriptor</firstterm>
	    <filename>j</filename></para>
	 <para>
            <command>&gt;&amp;2 </command>
         <link linkend="redirouterror2">Redirect
	    <filename>stdout</filename></link> of a command to
	    <filename>stderr</filename></para>
	 <para>
            <command>2&gt;&amp;1 </command>
         <link linkend="ioredirectionref1">Redirect
	    <filename>stderr</filename></link>
	    to <filename>stdout</filename></para>
	 <para>
            <command>&amp;&gt; </command>
         <link linkend="redirouterror">Redirect
	    <emphasis>both</emphasis> <filename>stdout</filename>
	    and <filename>stderr</filename></link> of a command to a
	    file</para>

	 <para><command>:&gt; <filename>file</filename></command>
         <link linkend="ioredirectionref">Truncate file</link>
          to zero length</para>
	  
	  </listitem>

         </itemizedlist>
	 </para>

<!-- ********************** -->

      <para><command>| </command>
         <link linkend="piperef">Pipe</link>, a device for passing the output
         of a command to another command or to the shell</para>
      <para><command>|| </command>
         <link linkend="orref">Logical OR test operator</link></para>

<!-- ********************** -->

      <para><command>- </command> (dash)
         <itemizedlist>

	 <listitem><para>
        <link linkend="defparam1">Prefix to <firstterm>default
	  parameter</firstterm></link>, in <firstterm>parameter
	  substitution</firstterm></para></listitem>
	 <listitem><para>
        <link linkend="dashref">Prefix to <firstterm>option
          flag</firstterm></link></para></listitem>

	 <listitem><para>
        <link linkend="dashref2">Indicating
        <firstterm>redirection</firstterm></link> from
        <filename>stdin</filename> or <filename>stdout</filename>
          </para></listitem>

	 <listitem>
	   <para><command>-- </command> (double-dash)</para>
           <para><link linkend="doubledashref">Prefix to
	     <firstterm>long</firstterm> command options</link></para>
	 <para>
         <link linkend="plusplusref"><firstterm>C-style</firstterm>
	 variable decrement</link> within <firstterm>double
	 parentheses</firstterm>
          </para></listitem>

         </itemizedlist>
	 </para>

<!-- ********************** -->

      <para><command>; </command> (semicolon)
	   <itemizedlist>
      <listitem><para><link linkend="semicolonref">As command
        separator</link></para></listitem>
      <listitem><para><command>\; </command>
         <link linkend="findref0"><firstterm>Escaped</firstterm> semicolon</link>,
	 terminates a <link linkend="findref">find</link>
	 command</para></listitem>
      <listitem><para><command>;; </command>
         <link linkend="doublesemicolon">Double-semicolon</link>, terminator in a
         <link linkend="caseesac1">case</link> option</para></listitem>

      <listitem>
        <para>Required when ...</para>
	<para><link linkend="needsemicolon"><firstterm>do</firstterm>
         keyword is on the first line of
	 <firstterm>loop</firstterm></link></para>
        <para><link linkend="omitsemicolon">
         terminating <firstterm>curly-bracketed</firstterm>
	 code block</link></para>
      </listitem>

	   </itemizedlist></para>

      <para><command>: </command>
         <link linkend="nullref">Colon</link>, <firstterm>null</firstterm>
	 command, equivalent to the
         <link linkend="trueref">true</link> Bash builtin
	   <itemizedlist>
	 <listitem><para>
            <command>:&gt; <filename>file</filename></command>
         <link linkend="ioredirectionref">Truncate file</link>
          to zero length</para></listitem>
	   </itemizedlist></para>

      <para><command>! </command>
         <link linkend="notref">Negation operator</link>, inverts <link
	 linkend="exitstatusref">exit status</link> of a test or command
           <itemizedlist>
      <listitem><para><command>!= </command>
         <link linkend="notequal">not-equal-to</link>
	 String comparison operator</para></listitem>
           </itemizedlist></para>

<!-- ********************** -->
      <para><command>? </command> (question mark)
         <itemizedlist>

      <listitem><para>
        <link linkend="quexregex">Match zero or one characters</link>,
	in an <link linkend="extregex"> Extended Regular
	Expression</link></para></listitem>
      <listitem><para><link linkend="quexwc">Single-character
	<firstterm>wild card</firstterm></link>,
	in <link linkend="globbingref">globbing</link></para></listitem>
        <listitem><para>In a
        <link linkend="cstrinary"><firstterm>C</firstterm>-style
        Trinary operator</link></para></listitem>

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


      <para><command>// </command>
        <link linkend="doubleslashref">Double forward slash</link>,
          behavior of <link
          linkend="cdref">cd</link> command toward</para>

<!-- ********************** -->

      <para><command>. </command> (dot / period)
         <itemizedlist>

	 <listitem><para>
            <command>. </command>
         <link linkend="dotref">Load a file</link> (into a script),
         equivalent to <link
         linkend="sourceref">source</link> command
	 </para></listitem>

	 <listitem><para>
            <command>. </command>
         <link linkend="regexdot">Match single character</link>,
         in a <link linkend="regexref">Regular Expression</link>
	 </para></listitem>

	 <listitem><para>
            <command>. </command>
         <link linkend="dotdirectory">Current working
         directory</link>
	 </para>
	 <para>
            <command>./ </command>
         <link linkend="currentwdref">Current working
          directory</link>
	 </para></listitem>

	 <listitem><para>
            <command>.. </command>
         <link linkend="dotdirectory"><firstterm>Parent</firstterm>
         directory</link>
	 </para></listitem>

         </itemizedlist>
	 </para>

<!-- ********************** -->

      <para><command>' ... '</command>
	 (single quotes)
         <link linkend="snglquo"><firstterm>strong</firstterm>