xrefindex.html

Shall高级编程

></LI
></UL
></P
><P
><B
CLASS="COMMAND"
>[[ ... ]]</B
>
         <A
HREF="tests.html#DBLBRACKETS"
>Double brackets</A
>,
	 extended <I
CLASS="FIRSTTERM"
>test</I
> construct</P
><P
><B
CLASS="COMMAND"
>$ </B
>
        <A
HREF="regexp.html#DOLLARSIGNREF"
><I
CLASS="FIRSTTERM"
>Anchor</I
></A
>,
          in a <A
HREF="regexp.html#REGEXREF"
>Regular Expression</A
></P
><P
><B
CLASS="COMMAND"
>$ </B
>
         <A
HREF="variables.html#VARSUBN"
>Prefix to a variable name</A
></P
><P
><B
CLASS="COMMAND"
>$( ... ) </B
>
         <A
HREF="varassignment.html#COMMANDSUBREF0"
>Command substitution</A
>,
	 setting a variable with output of a command,
	 using parentheses notation</P
><P
><B
CLASS="COMMAND"
>` ... ` </B
>
         <A
HREF="commandsub.html#BACKQUOTESREF"
>Command substitution</A
>,
	 using <A
HREF="special-chars.html#BACKTICKSREF"
>backquotes</A
>
	 notation</P
><P
><B
CLASS="COMMAND"
>${ ... }</B
> Variable manipulation / evaluation

         <UL
><LI
><P
><B
CLASS="COMMAND"
>${var}</B
>
      <A
HREF="parameter-substitution.html#PSSUB1"
>Value of a variable</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${#var}</B
>
      <A
HREF="parameter-substitution.html#PSOREX1"
>Length of a variable</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${#@}</B
></P
><P
><B
CLASS="COMMAND"
>${#*}</B
>
        <A
HREF="parameter-substitution.html#NUMPOSPARAM"
>Number of
	 <I
CLASS="FIRSTTERM"
>positional
	 parameters</I
></A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${parameter?err_msg}</B
>
         <A
HREF="parameter-substitution.html#QERRMSG"
>Parameter-unset
        message</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${parameter-default}</B
></P
><P
><B
CLASS="COMMAND"
>${parameter:-default}</B
></P
><P
><B
CLASS="COMMAND"
>${parameter=default}</B
></P
><P
><B
CLASS="COMMAND"
>${parameter:=default}</B
>
      <A
HREF="parameter-substitution.html#DEFPARAM1"
>Set default
      parameter</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${parameter+alt_value}</B
></P
><P
><B
CLASS="COMMAND"
>${parameter:+alt_value}</B
></P
><P
><A
HREF="parameter-substitution.html#PARAMALTV"
>Alternate value</A
>
          of parameter, if set</P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${!var}</B
></P
><P
><A
HREF="ivr.html#IVR2"
>Indirect referencing of a variable</A
>,
	   new notation</P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${!varprefix*}</B
></P
><P
><B
CLASS="COMMAND"
>${!varprefix@}</B
></P
><P
><A
HREF="parameter-substitution.html#VARPREFIXM"
>Match
        <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>names</I
></SPAN
></A
> of all previously declared
        variables beginning with <TT
CLASS="VARNAME"
>varprefix</TT
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${string:position}</B
></P
><P
><B
CLASS="COMMAND"
>${string:position:length}</B
>
      <A
HREF="string-manipulation.html#SUBSTREXTR01"
>Substring
      extraction</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${var#Pattern}</B
></P
><P
><B
CLASS="COMMAND"
>${var##Pattern}</B
>
      <A
HREF="parameter-substitution.html#PSOREX2"
>Substring
      removal</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${var%Pattern}</B
></P
><P
><B
CLASS="COMMAND"
>${var%%Pattern}</B
>
      <A
HREF="parameter-substitution.html#PCTPATREF"
>Substring
        removal</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>${string/substring/replacement}</B
></P
><P
><B
CLASS="COMMAND"
>${string//substring/replacement}</B
></P
><P
><B
CLASS="COMMAND"
>${string/#substring/replacement}</B
></P
><P
><B
CLASS="COMMAND"
>${string/%substring/replacement}</B
>
      <A
HREF="string-manipulation.html#SUBSTRREPL00"
>Substring
      replacement</A
></P
></LI
></UL
></P
><P
><B
CLASS="COMMAND"
>\ </B
>
         <A
HREF="escapingsection.html#ESCP"
>Escape</A
> the character following
	    <UL
><LI
><P
><B
CLASS="COMMAND"
>\&#60; ... \&#62; </B
>
         <A
HREF="regexp.html#ANGLEBRAC"
>Angle brackets</A
>,
         <I
CLASS="FIRSTTERM"
>escaped</I
>,
	 word boundary in a <A
HREF="regexp.html#REGEXREF"
>Regular
	 Expression</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>\{ N \}</B
>
         <A
HREF="regexp.html#ESCPCB"
><SPAN
CLASS="QUOTE"
>"Curly"</SPAN
> brackets</A
>,
         <I
CLASS="FIRSTTERM"
>escaped</I
>,
	 number of character sets to match in an <A
HREF="regexp.html#EXTREGEX"
>Extended RE</A
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
>\; </B
>
         <A
HREF="moreadv.html#FINDREF0"
><I
CLASS="FIRSTTERM"
>Semicolon</I
></A
>,
         <I
CLASS="FIRSTTERM"
>escaped</I
>,
	 terminates a <A
HREF="moreadv.html#FINDREF"
>find</A
>
	 command</P
></LI
><LI
><P
><B
CLASS="COMMAND"
>\$$ </B
> <A
HREF="ivr.html#IVRREF"
>Indirect
        reverencing of a variable</A
>, old-style notation</P
></LI
><LI
><P
><A
HREF="escapingsection.html#ESCNEWLINE"
>Escaping
        a <I
CLASS="FIRSTTERM"
>newline</I
></A
>,
	to write a multi-line command</P
></LI
></UL
></P
><P
><B
CLASS="COMMAND"
>&#38; </B
>
         <UL
><LI
><P
>            <B
CLASS="COMMAND"
>&#38;&#62; </B
>
         <A
HREF="special-chars.html#REDIROUTERROR"
>Redirect
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>both</I
></SPAN
> <TT
CLASS="FILENAME"
>stdout</TT
>
	    and <TT
CLASS="FILENAME"
>stderr</TT
></A
> of a command to a
	    file</P
></LI
><LI
><P
>            <B
CLASS="COMMAND"
>&#62;&#38;j </B
>
            <A
HREF="io-redirection.html#IOREDIRECTIONREF1"
>Redirect
	    <TT
CLASS="FILENAME"
>stdout</TT
></A
> to
	    <I
CLASS="FIRSTTERM"
>file descriptor</I
>
	    <I
CLASS="FIRSTTERM"
>j</I
></P
><P
>            <B
CLASS="COMMAND"
>&#62;&#38;2 </B
>
         <A
HREF="special-chars.html#REDIROUTERROR2"
>Redirect
	    <TT
CLASS="FILENAME"
>stdout</TT
></A
> of a command to
	    <TT
CLASS="FILENAME"
>stderr</TT
></P
></LI
><LI
><P
>            <B
CLASS="COMMAND"
>i&#62;&#38;j </B
>
            <A
HREF="io-redirection.html#IOREDIRECTIONREF1"
>Redirect
	    <I
CLASS="FIRSTTERM"
>file descriptor</I
></A
>
	    <I
CLASS="FIRSTTERM"
>i</I
> to
	    <I
CLASS="FIRSTTERM"
>file descriptor</I
>
	    <I
CLASS="FIRSTTERM"
>j</I
></P
><P
>            <B
CLASS="COMMAND"
>2&#62;&#38;1 </B
>
         <A
HREF="io-redirection.html#IOREDIRECTIONREF1"
>Redirect
	    <TT
CLASS="FILENAME"
>stderr</TT
></A
> to
	    <TT
CLASS="FILENAME"
>stdout</TT
></P
></LI
><LI
><P
><A
HREF="io-redirection.html#CFD"
>Closing <I
CLASS="FIRSTTERM"
>file
      descriptors</I
></A
></P
><P
><B
CLASS="COMMAND"
>n&#60;&#38;-</B
>
           Close input file descriptor
	   <I
CLASS="FIRSTTERM"
>n</I
></P
><P
><B
CLASS="COMMAND"
>0&#60;&#38;-</B
>,
	   <B
CLASS="COMMAND"
>&#60;&#38;-</B
>
           Close <TT
CLASS="FILENAME"
>stdin</TT
></P
><P
><B
CLASS="COMMAND"
>n&#62;&#38;-</B
>
          Close output file descriptor
	  <I
CLASS="FIRSTTERM"
>n</I
></P
><P
><B
CLASS="COMMAND"
>1&#62;&#38;-</B
>,
	   <B
CLASS="COMMAND"
>&#62;&#38;-</B
>
	   Close <TT
CLASS="FILENAME"
>stdout</TT
></P
></LI
><LI
><P
>	    <B
CLASS="COMMAND"
>&#38;&#38; </B
>
	    <A
HREF="special-chars.html#LOGICALAND"
>Logical AND
	    test operator</A
></P
></LI
><LI
><P
>	    <B
CLASS="COMMAND"
>Command &#38;</B
>
	    <A
HREF="special-chars.html#BGJOB"
>Run job in
            <I
CLASS="FIRSTTERM"
>background</I
></A
></P
></LI
></UL
></P
><P
><B
CLASS="COMMAND"
># </B
>
         <A
HREF="special-chars.html#HASHMARKREF"
>Hashmark</A
>,
         special symbol beginning a script
         <I
CLASS="FIRSTTERM"
>comment</I
></P
><P
><B
CLASS="COMMAND"
>#!</B
>
         <A
HREF="sha-bang.html#SHABANGREF"
>Sha-bang</A
>,
         special string starting a
         <A
HREF="part1.html#WHATSASCRIPT"
>shell script</A
></P
><P
><B
CLASS="COMMAND"
>* </B
> Asterisk
         <UL
><LI
><P
>         <A
HREF="special-chars.html#ASTERISKREF"
><I
CLASS="FIRSTTERM"
>Wild
         card</I
></A
>,
	 in <A
HREF="globbingref.html"
>globbing</A
>
	 </P
></LI
><LI
><P
>         <A
HREF="special-chars.html#ASTERISKREF2"
>Any number of characters</A
>
	 in a <A
HREF="regexp.html#REGEXREF"
>Regular Expression</A
>
	 </P
></LI
><LI
><P
>            <B
CLASS="COMMAND"
> ** </B
>
         <A
HREF="operations.html#EXPONENTIATIONREF"
>Exponentiation</A
>,
	 arithmetic operator
	 </P
></LI
></UL
>
	 </P
><P
><B
CLASS="COMMAND"
>% </B
> Percent sign
         <UL
><LI
><P
>         <A
HREF="operations.html#MODULOREF"
>Modulo</A
>, division-remainder
         arithmetic operation
	 </P
></LI
><LI
><P
>         <A
HREF="parameter-substitution.html#PCTPATREF"
>Substring removal</A
>
	   (pattern matching) operator</P
></LI
></UL
>
	 </P
><P
><B
CLASS="COMMAND"
>+ </B
> Plus sign
         <UL
><LI
><P
><A
HREF="regexp.html#PLUSREF"
><I
CLASS="FIRSTTERM"
>Character
           match</I
></A
>, in an <A
HREF="regexp.html#EXTREGEX"
>extended Regular
           Expression</A
></P
></LI
><LI
><P
><A
HREF="parameter-substitution.html#PARAMALTV"
>Prefix to
	   <I
CLASS="FIRSTTERM"
>alternate parameter</I
></A
>, in
	   <I
CLASS="FIRSTTERM"
>parameter substitution</I
></P
></LI
><LI
><P
><B
CLASS="COMMAND"
> ++ </B
>
           <A
HREF="dblparens.html#PLUSPLUSREF"
><I
CLASS="FIRSTTERM"
>C-style</I
>
           variable increment</A
>, within <I
CLASS="FIRSTTERM"
>double
           parentheses</I
></P
></LI
></UL
></P
><P
>* * *</P
><P
><I
CLASS="FIRSTTERM"
>Shell Variables</I
></P
><P
><B
CLASS="COMMAND"
>$_ </B
>
        <A
HREF="variables2.html#UNDERSCOREREF"
>Last argument to previous
	command</A
></P
><P
><B
CLASS="COMMAND"
>$- </B
>
        <A
HREF="variables2.html#FLPREF"
>Flags passed to script</A
>, using <A
HREF="internal.html#SETREF"
>set</A
></P
><P
><B
CLASS="COMMAND"
>$! </B
>
         <A
HREF="variables2.html#PIDVARREF"
><I
CLASS="FIRSTTERM"
>Process ID</I
>
         of last background job</A
></P
><P
><B
CLASS="COMMAND"
>$? </B
>
         <A
HREF="exit-status.html#EXSREF"
><I
CLASS="FIRSTTERM"
>Exit
         status</I
> of a command</A
></P
><P
><B
CLASS="COMMAND"
>$@ </B
>
         All the <I
CLASS="FIRSTTERM"
>positional parameters</I
>, <A
HREF="variables2.html#APPREF2"
>as <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>separate</I
></SPAN
>
         words</A
></P
><P
><B
CLASS="COMMAND"
> $* </B
>
         All the <I
CLASS="FIRSTTERM"
>positional parameters</I
>, <A
HREF="variables2.html#APPREF"
>as a <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>single</I
></SPAN
>
         word</A
></P
><P
><B
CLASS="COMMAND"
>$$ </B
>
         <A
HREF="special-chars.html#PROCESSIDREF"
>Process ID</A
> of the
         script</P
><P
><B
CLASS="COMMAND"
>$# </B
>
         <A
HREF="variables2.html#CLACOUNTREF"
>Number of arguments passed</A
> to a
         <A
HREF="functions.html#FUNCTIONREF"
>function</A
>, or to the script
         itself</P
><P
><B
CLASS="COMMAND"
>$0 </B
>
         <A
HREF="othertypesv.html#SCRNAMEPARAM"
>Filename of the script</A
></P
><P
><B
CLASS="COMMAND"
>$1 </B
>
         <A
HREF="othertypesv.html#POSPARAMREF1"
>First argument passed to script</A
></P
><P
><B
CLASS="COMMAND"
>$9 </B
>
         <A
HREF="othertypesv.html#POSPARAMREF1"
>Ninth argument passed to script</A
></P
><P
><A
HREF="refcards.html#SPECSHVARTAB"
><B
CLASS="COMMAND"
>Table</B
></A
>
        of <I
CLASS="FIRSTTERM"
>shell variables</I
></P
><P
>* * * * * *</P
><P
><B
CLASS="COMMAND"
>-a </B
>
        <A
HREF="comparison-ops.html#COMPOUNDAND"
>Logical AND</A
>
	compound comparison test</P
><P
><I
CLASS="FIRSTTERM"
>Advanced Bash Scripting Guide</I
>,
         <A
HREF="index.html#WHERE_TARBALL"
>where to download</A
></P
><P
><A
HREF="aliases.html#ALIASREF"
>Alias</A
>
         <UL
><LI
><P
><A
HREF="aliases.html#UNALIASREF"
>Removing an
        <I
CLASS="FIRSTTERM"
>alias</I
></A
>, using
	<I
CLASS="FIRSTTERM"
>unalias</I
></P
></LI
></UL
></P
><P
><A
HREF="list-cons.html#LCONS1"
><I
CLASS="FIRSTTERM"
>And</I
> list</A
>
         <UL
><LI
><P
>         <A
HREF="list-cons.html#ANDDEFAULT"
>To supply default command-line
         argument</A
></P
></LI
></UL
></P
><P
><A
HREF="regexp.html#ANGLEBRAC"
>Angle brackets</A
>,
         <I
CLASS="FIRSTTERM"
>escaped</I
>,
	 <B
CLASS="COMMAND"
>\&#60; . . . \&#62; </B
>
	 word boundary in a <A
HREF="regexp.html#REGEXREF"
>Regular
	 Expression</A
></P
><P
><A
HREF="here-docs.html#ANONHEREDOC0"
>Anonymous
         <I
CLASS="FIRSTTERM"
>here document</I
></A
>, using
         <B
CLASS="COMMAND"
>:</B
></P
><P
><A
HREF="filearchiv.html#FAARCHIVING1"
>Archiving</A
>
         <UL
><LI
><P
><A
HREF="filearchiv.html#RPMREF"
>rpm</A
></P
></LI
><LI
><P
><A
HREF="filearchiv.html#TARREF"
>tar</A
></P
></LI
></UL
></P
><P
><A
HREF="arithexp.html#ARITHEXPREF"
>Arithmetic expansion</A
>
         <UL
><LI
><P
><A
HREF="arithexp.html#ARITHEXPVAR1"
>         variations of</A
></P
></LI
></UL
></P
><P
><A
HREF="operations.html#AROPS1"
>Arithmetic operators</A
>
         <UL
><LI
><P
><A
HREF="operations.html#ARITHOPSCOMB"
>         combination operators</A
>, <I
CLASS="FIRSTTERM"
>C</I
>-style</P
><P
><B
CLASS="COMMAND"
> += </B
>
	       <B
CLASS="COMMAND"
> -= </B
>
	       <B
CLASS="COMMAND"
> *= </B
>
               <B
CLASS="COMMAND"
> /= </B
>
	       <B
CLASS="COMMAND"
> %= </B
>
	 </P
><DIV
CLASS="NOTE"
><TABLE
CLASS="NOTE"
WIDTH="90%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="common/note.png"
HSPACE="5"
ALT="Note"></TD
><TD
ALIGN="LEFT"