xrefindex.html

Shall高级编程

VALIGN="TOP"
><P
><A
HREF="bashver3.html#PLUSEQSTR"
>In certain contexts</A
>,
	   <B
CLASS="COMMAND"
>+=</B
> can also function as a <I
CLASS="FIRSTTERM"
>string
	   concatenation</I
> operator.</P
></TD
></TR
></TABLE
></DIV
></LI
></UL
></P
><P
><A
HREF="arrays.html#ARRAYREF"
>Arrays</A
></P
><UL
><LI
><P
><A
HREF="arrays.html#ARRAYREF"
>Bracket notation</A
>
	      </P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYAPPEND0"
>Concatenating</A
>,
	      <I
CLASS="FIRSTTERM"
>example script</I
></P
></LI
><LI
><P
><A
HREF="arrays.html#COPYARRAY0"
>Copying</A
>
	      </P
></LI
><LI
><P
><A
HREF="declareref.html#ARRAYDECLARE"
>Declaring</A
></P
><P
><TT
CLASS="VARNAME"
>declare -a
		 array_name</TT
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYINDIR"
>Embedded
	     arrays</A
></P
></LI
><LI
><P
><A
HREF="arrays.html#EMPTYARRAY0"
>Empty
	     arrays, empty elements</A
>, <I
CLASS="FIRSTTERM"
>example
	     script</I
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYINDIR"
>Indirect references</A
>
	      </P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYINIT0"
>Initialization</A
></P
><P
><TT
CLASS="VARNAME"
>array=( element1 element2 ... elementN)</TT
></P
><P
><A
HREF="arrays.html#ARRAYASSIGN0"
><I
CLASS="FIRSTTERM"
>Example
	        script</I
></A
></P
><P
>Using <A
HREF="arrays.html#ARRAYINITCS"
>command
	         substitution</A
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYINITCS"
>Loading a
	     file</A
> into an array</P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYMULTIDIM"
>Multidimensional</A
>,
              simulating</P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYNEST"
>Nesting and
	      embedding</A
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYNOTATION"
>Notation
	      and usage</A
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYNUMELEMENTS"
>Number of elements in</A
></P
><P
><TT
CLASS="VARNAME"
>${#array_name[@]}</TT
></P
><P
><TT
CLASS="VARNAME"
>${#array_name[*]}</TT
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYSYNTAX"
>Operations</A
></P
></LI
><LI
><P
><A
HREF="assortedtips.html#PASSARRAY"
>Passing
             an <I
CLASS="FIRSTTERM"
>array</I
></A
> to a
             function</P
></LI
><LI
><P
>As <A
HREF="assortedtips.html#RETARRAY"
>              <I
CLASS="FIRSTTERM"
>return value</I
> from
	      a function</A
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYSPECIALPROPS"
>Special properties</A
>,
	     <I
CLASS="FIRSTTERM"
>example script</I
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYSTRINGOPS"
>String operations</A
>,
	     <I
CLASS="FIRSTTERM"
>example script</I
></P
></LI
><LI
><P
><A
HREF="arrays.html#ARRAYUNSET"
><I
CLASS="FIRSTTERM"
>unset</I
> deletes array
	     elements</A
></P
></LI
></UL
><P
><A
HREF="asciitable.html"
>ASCII table</A
></P
><P
><A
HREF="awk.html"
>awk</A
> field-oriented text
         processing language
         <UL
><LI
><P
><A
HREF="randomvar.html#AWKRANDOMREF"
>         <TT
CLASS="VARNAME"
>rand()</TT
></A
>,
	 random function</P
></LI
><LI
><P
><A
HREF="string-manipulation.html#AWKSTRINGMANIP2"
>String
        manipulation</A
></P
></LI
><LI
><P
><A
HREF="internal.html#EXPORTAWK"
>Using
	<I
CLASS="FIRSTTERM"
>export</I
></A
> to pass a variable to an
	embedded <I
CLASS="FIRSTTERM"
>awk</I
> script</P
></LI
></UL
></P
><P
>* * *</P
><P
><A
HREF="special-chars.html#BACKTICKSREF"
>Backquotes</A
>,
         used in <A
HREF="commandsub.html#BACKQUOTESREF"
>command
         substitution</A
></P
><P
><A
HREF="mathc.html#BASE0"
>Base conversion</A
>,
        <I
CLASS="FIRSTTERM"
>example script</I
></P
><P
><A
HREF="why-shell.html#BASHDEF"
>Bash</A
>
         <UL
><LI
><P
><A
HREF="gotchas.html#BASH3GOTCHA"
>Bad scripting
         practices</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#BASICSREV0"
>Basics reviewed</A
>,
        <I
CLASS="FIRSTTERM"
>script example</I
></P
></LI
><LI
><P
><A
HREF="bash-options.html#CLOPTS"
>Command-line
          options</A
></P
><P
><A
HREF="options.html#OPTIONSTABLE"
><B
CLASS="COMMAND"
>Table</B
></A
></P
></LI
><LI
><P
> <A
HREF="portabilityissues.html#BASHCOMPAT"
>Features that classic
        <I
CLASS="FIRSTTERM"
>Bourne</I
> shell lacks</A
></P
></LI
><LI
><P
><A
HREF="variables2.html#INTERNALVARIABLES"
>Internal variables</A
></P
></LI
><LI
><P
><A
HREF="bash2.html#BASH2REF"
>        Version 2</A
></P
></LI
><LI
><P
><A
HREF="bashver3.html#BASH3REF"
>        Version 3</A
></P
></LI
></UL
></P
><P
><A
HREF="sample-bashrc.html"
>.bashrc</A
></P
><P
><A
HREF="variables2.html#BASHSUBSHELLREF"
><TT
CLASS="VARNAME"
>$BASH_SUBSHELL</TT
></A
></P
><P
><A
HREF="external.html#BASICCOMMANDS1"
>Basic commands</A
>, external</P
><P
><A
HREF="timedate.html#BATCHPROCREF"
>Batch processing</A
></P
><P
><A
HREF="mathc.html#BCREF"
>bc</A
>, calculator utility
         <UL
><LI
><P
><A
HREF="mathc.html#BCHEREDOC"
>In a <I
CLASS="FIRSTTERM"
>here
        document</I
></A
></P
></LI
><LI
><P
><A
HREF="mathc.html#BCTEMPLATE"
>Template</A
>
        for calculating a script variable</P
></LI
></UL
></P
><P
><A
HREF="biblio.html"
>Bibliography</A
></P
><P
><A
HREF="textproc.html#BISONREF"
>Bison</A
> utility</P
><P
><A
HREF="operations.html#BITWSOPS1"
>Bitwise operators</A
></P
><P
><A
HREF="special-chars.html#CODEBLOCKREF"
>Blocks of code</A
>
         <UL
><LI
><P
><A
HREF="special-chars.html#BLOCKIO"
>Redirection</A
></P
><P
><A
HREF="special-chars.html#BLOCKIO2"
><I
CLASS="FIRSTTERM"
>Script
        example</I
></A
>:
	redirecting output of a a code block</P
></LI
></UL
></P
><P
><A
HREF="special-chars.html#BRACEEXPREF"
>Brace expansion</A
>
         <UL
><LI
><P
><A
HREF="special-chars.html#BRACEEXPREF33"
>Extended</A
>,
	   <TT
CLASS="REPLACEABLE"
><I
>{a..z}</I
></TT
></P
></LI
></UL
></P
><P
>Brackets, <B
CLASS="COMMAND"
>[ ]</B
>
         <UL
><LI
><P
><A
HREF="arrays.html#BRACKARRAY"
><I
CLASS="FIRSTTERM"
>Array</I
>
        element</A
></P
></LI
><LI
><P
><A
HREF="regexp.html#BRACKETSREF"
>Enclose character set
        to match</A
> in a <I
CLASS="FIRSTTERM"
>Regular
	Expression</I
></P
></LI
><LI
><P
><A
HREF="special-chars.html#BRACKTEST"
><I
CLASS="FIRSTTERM"
>Test</I
> construct</A
></P
></LI
></UL
></P
><P
>Brackets, <I
CLASS="FIRSTTERM"
>curly</I
>, <B
CLASS="COMMAND"
>{}</B
>,
        used in</P
><UL
><LI
><P
><A
HREF="special-chars.html#CODEBLOCKREF"
>Code
        block</A
></P
></LI
><LI
><P
><A
HREF="moreadv.html#CURLYBRACKETSREF"
>         <I
CLASS="FIRSTTERM"
>find</I
></A
></P
></LI
><LI
><P
><A
HREF="regexp.html#ESCPCB"
><I
CLASS="FIRSTTERM"
>Extended Regular
	 Expressions</I
></A
></P
></LI
><LI
><P
><A
HREF="othertypesv.html#BRACKETNOTATION"
><I
CLASS="FIRSTTERM"
>Positional
        parameters</I
></A
></P
></LI
><LI
><P
><A
HREF="moreadv.html#XARGSCURLYREF"
><I
CLASS="FIRSTTERM"
>xargs</I
></A
></P
></LI
></UL
><P
><A
HREF="loopcontrol.html#BRKCONT1"
>break</A
>
         <I
CLASS="FIRSTTERM"
>loop</I
> control command
	    <UL
><LI
><P
><A
HREF="loopcontrol.html#BREAKPARAM"
>Parameter</A
>
         (optional)</P
></LI
></UL
></P
><P
><A
HREF="internal.html#BUILTINREF"
>Builtins</A
> in
         <I
CLASS="FIRSTTERM"
>Bash</I
>
	    <UL
><LI
><P
><A
HREF="internal.html#BLTINFRK"
>Do not fork a subprocess</A
>
         </P
></LI
></UL
></P
><P
>* * *</P
><P
><A
HREF="testbranch.html#CASEESAC1"
><I
CLASS="FIRSTTERM"
>case</I
>
         construct</A
>
	    <UL
><LI
><P
><A
HREF="testbranch.html#CASECL"
>Command-line parameters</A
>,
         handling</P
></LI
><LI
><P
><A
HREF="testbranch.html#CSGLOB"
>Globbing</A
>,
         filtering strings with</P
></LI
></UL
></P
><P
><A
HREF="external.html#CATREF"
>cat</A
>,
        con<I
CLASS="FIRSTTERM"
>cat</I
>entate file(s)
	    <UL
><LI
><P
><A
HREF="optimizations.html#CATABUSE"
>Abuse of</A
></P
></LI
><LI
><P
><A
HREF="here-docs.html#CATSCRIPTREF"
><I
CLASS="FIRSTTERM"
>cat</I
>
         scripts</A
></P
></LI
><LI
><P
><A
HREF="external.html#CATLESSEFF"
>Less efficient than
        redirecting <TT
CLASS="FILENAME"
>stdin</TT
></A
></P
></LI
><LI
><P
><A
HREF="internal.html#READPIPEREF"
>Piping the output
        of</A
>, to a <A
HREF="internal.html#READREF"
>read</A
></P
></LI
><LI
><P
><A
HREF="external.html#CATUSES"
>Uses of</A
></P
></LI
></UL
></P
><P
><A
HREF="othertypesv.html#CHILDREF"
>Child processes</A
></P
><P
><A
HREF="special-chars.html#NULLREF"
>Colon</A
>, <B
CLASS="COMMAND"
>: </B
>,
         equivalent to the <A
HREF="internal.html#TRUEREF"
>true</A
> Bash
         builtin</P
><P
><A
HREF="colorizing.html#COLORIZINGREF"
>Colorizing scripts</A
>
	    <UL
><LI
><P
><A
HREF="colorizing.html#COLORIZTABLE"
><B
CLASS="COMMAND"
>Table</B
></A
> of
	   color escape sequences</P
></LI
><LI
><P
><A
HREF="colorizing.html#COLORIZTEMPL"
>Template</A
>,
	   colored text on colored background</P
></LI
></UL
></P
><P
><A
HREF="operations.html#COMMAOP"
>Comma operator</A
>,
         linking commands or operations</P
><P
><A
HREF="bash-options.html"
>Command-line options</A
></P
><P
><A
HREF="commandsub.html#COMMANDSUBREF"
>Command substitution</A
>
         <UL
><LI
><P
>         <A
HREF="commandsub.html#CSPARENS"
><B
CLASS="COMMAND"
>$( ... )</B
></A
>,
	   preferred notation</P
></LI
><LI
><P
><A
HREF="commandsub.html#BACKQUOTESREF"
><I
CLASS="FIRSTTERM"
>Backquotes</I
></A
></P
></LI
><LI
><P
><A
HREF="commandsub.html#CSTOOLSET"
>Extending the
         <I
CLASS="FIRSTTERM"
>Bash</I
> toolset</A
></P
></LI
><LI
><P
><A
HREF="commandsub.html#CSSUBSH"
>Invokes a
         <I
CLASS="FIRSTTERM"
>subshell</I
></A
></P
></LI
><LI
><P
><A
HREF="commandsub.html#CSNEST"
>Nesting</A
></P
></LI
><LI
><P
><A
HREF="commandsub.html#CSTRNL"
>Removes trailing newlines</A
>
         </P
></LI
><LI
><P
><A
HREF="commandsub.html#CSVL"
>Setting variable from loop output</A
>
         </P
></LI
><LI
><P
><A
HREF="commandsub.html#CSWS"
>Word splitting</A
></P
></LI
></UL
></P
><P
><A
HREF="assortedtips.html#COMMENTH"
>Comment headers</A
>,
        special purpose</P
><P
>Commenting out blocks of code
        <UL
><LI
><P
>Using an <A
HREF="here-docs.html#CBLOCK1"
><I
CLASS="FIRSTTERM"
>anonymous</I
> here
        document</A
></P
></LI
><LI
><P
>Using an <A
HREF="assortedtips.html#COMOUTBL"
>        <I
CLASS="FIRSTTERM"
>if-then</I
> construct</A
></P
></LI
></UL
></P
><P
><A
HREF="comparison-ops.html#CCOMPARISON1"
>Compound comparison</A
>
         operators</P
><P
><A
HREF="filearchiv.html#FACOMPRESSION1"
>Compression utilities</A
>
         <UL
><LI
><P
><A
HREF="filearchiv.html#BZIPREF"
>bzip2</A
></P
></LI
><LI
><P
><A
HREF="filearchiv.html#COMPRESSREF"
>compress</A
></P
></LI
><LI
><P
><A
HREF="filearchiv.html#GZIPREF"
>gzip</A
></P
></LI
><LI
><P
><A
HREF="filearchiv.html#ZIPREF"
>zip</A
></P
></LI
></UL
></P
><P
><A
HREF="loopcontrol.html#BRKCONT1"
>continue</A
> loop control command</P
><P
><A
HREF="special-chars.html#CONTROLCHARREF"
>Control characters</A
>
         <UL
><LI
><P
><A
HREF="special-chars.html#CTLCREF"
>Control-C</A
>,
         <I
CLASS="FIRSTTERM"
>break</I
></P
></LI
><LI
><P
><A
HREF="special-chars.html#CTLDREF"
>Control-D</A
>,
         terminate / log out / erase</P
></LI
><LI
><P
><A
HREF="special-chars.html#CTLGREF"
>Control-G</A
>,
         <TT
CLASS="USERINPUT"
><B
>BEL</B
></TT
>
         (<I
CLASS="FIRSTTERM"
>beep</I
>)</P
></LI
><LI
><P
><A
HREF="special-chars.html#CTLHREF"
>Control-H</A
>,
         <I
CLASS="FIRSTTERM"
>rubout</I
></P
></LI
><LI
><P
><A
HREF="special-chars.html#CTLJREF"
>Control-J</A
>,
         <I
CLASS="FIRSTTERM"
>newline</I
></P
></LI
><LI
><P
><A
HREF="special-chars.html#CTLMREF"
>Control-M</A
>,
         carriage return</P
></LI
></UL
></P
><P
><A
HREF="system.html#CRONREF"
>cron</A
>, scheduling
        <I
CLASS="FIRSTTERM"
>daemon</I
></P
><P
><A
HREF="assortedtips.html#CSTYLE"
><I
CLASS="FIRSTTERM"
>C</I
>-style syntax
        </A
>, for handling variables</P
><P
>Curly brackets {}
           <UL
><LI
><P
><A
HREF="moreadv.html#CURLYBRACKETSREF"
>in
         <I
CLASS="FIRSTTERM"
>find</I
> command</A
></P
></LI
><LI
><P
><A
HREF="regexp.html#ESCPCB"
>in an
         <I
CLASS="FIRSTTERM"
>Extended Regular
	 Expression</I
></A
></P
></LI
><LI
><P
><A
HREF="moreadv.html#XARGSCURLYREF"
>in
         <I
CLASS="FIRSTTERM"
>xargs</I
></A
></P
></LI
></UL
></P
><P
>* * *</P
><P
><A
HREF="communications.html#DAEMONREF"
>Daemons</A
>, in UNIX-type OS</P
><P
><A
HREF="timedate.html#DATEREF"
>date</A
></P
><P
><A
HREF="mathc.html#DCREF"
>dc</A
>, calculator utility</P
><P
><A
HREF="extmisc.html#DDREF"
>dd</A
>, <I
CLASS="FIRSTTERM"
>data
        duplicator</I
> command
	  <UL
><LI
><P
><A