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>Advanced Bash-Scripting Guide: An in-depth exploration of the art of shell scripting</TH
></TR
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HREF="loopcontrol.html"
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>Chapter 11. Loops and Branches</TD
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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="TESTBRANCH"
></A
>11.4. Testing and Branching</H1
><P
>The <B
CLASS="COMMAND"
>case</B
> and <B
CLASS="COMMAND"
>select</B
>
	  constructs are technically not loops, since they do not iterate the
	  execution of a code block. Like loops, however, they direct
	  program flow according to conditions at the top or bottom of
	  the block.</P
><DIV
CLASS="VARIABLELIST"
><P
><B
><A
NAME="CASEESAC1"
></A
>Controlling program flow in a code
	    block</B
></P
><DL
><DT
><B
CLASS="COMMAND"
>case (in) / esac</B
></DT
><DD
><P
>The <B
CLASS="COMMAND"
>case</B
> construct is the shell
	      scripting analog to <TT
CLASS="REPLACEABLE"
><I
>switch</I
></TT
>
	      in <B
CLASS="COMMAND"
>C/C++</B
>.
	      It permits branching to one of a number of code blocks,
	      depending on condition tests. It serves as a kind of
	      shorthand for multiple <SPAN
CLASS="TOKEN"
>if/then/else</SPAN
>
	      statements and is an appropriate tool for creating
	      menus.</P
><P
><P
><B
CLASS="COMMAND"
>case</B
>   "$<TT
CLASS="REPLACEABLE"
><I
>variable</I
></TT
>"   in <BR><BR>  "$<TT
CLASS="REPLACEABLE"
><I
>condition1</I
></TT
>" ) <BR>  <TT
CLASS="REPLACEABLE"
><I
>command</I
></TT
>... <BR>  ;; <BR><BR>  "$<TT
CLASS="REPLACEABLE"
><I
>condition2</I
></TT
>" ) <BR>  <TT
CLASS="REPLACEABLE"
><I
>command</I
></TT
>... <BR>  ;; <BR><BR><BR><B
CLASS="COMMAND"
>esac</B
> </P
></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"
VALIGN="TOP"
><P
>	      <UL
><LI
><P
>Quoting the variables is not mandatory,
		since word splitting does not take place.</P
></LI
><LI
><P
><A
NAME="CASEPAREN"
></A
>Each test line
                    ends with a right paren <B
CLASS="COMMAND"
>)</B
>.

  <A
NAME="AEN7087"
HREF="#FTN.AEN7087"
>[1]</A
>
			  </P
></LI
><LI
><P
>Each condition block ends
		with a <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>double</I
></SPAN
> semicolon
		<SPAN
CLASS="TOKEN"
>;;</SPAN
>.</P
></LI
><LI
><P
>If a condition tests
                <I
CLASS="FIRSTTERM"
>true</I
>, then the associated
		commands execute and the <B
CLASS="COMMAND"
>case</B
>
		block terminates.</P
></LI
><LI
><P
>The entire <B
CLASS="COMMAND"
>case</B
>
		block ends with an <B
CLASS="COMMAND"
>esac</B
>
		(<I
CLASS="WORDASWORD"
>case</I
> spelled backwards).</P
></LI
></UL
>
	    </P
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="EX29"
></A
><P
><B
>Example 11-25. Using <I
CLASS="FIRSTTERM"
>case</I
></B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# Testing ranges of characters.
   3&nbsp;
   4&nbsp;echo; echo "Hit a key, then hit return."
   5&nbsp;read Keypress
   6&nbsp;
   7&nbsp;case "$Keypress" in
   8&nbsp;  [[:lower:]]   ) echo "Lowercase letter";;
   9&nbsp;  [[:upper:]]   ) echo "Uppercase letter";;
  10&nbsp;  [0-9]         ) echo "Digit";;
  11&nbsp;  *             ) echo "Punctuation, whitespace, or other";;
  12&nbsp;esac      #  Allows ranges of characters in [square brackets],
  13&nbsp;          #+ or POSIX ranges in [[double square brackets.
  14&nbsp;
  15&nbsp;#  In the first version of this example,
  16&nbsp;#+ the tests for lowercase and uppercase characters were
  17&nbsp;#+ [a-z] and [A-Z].
  18&nbsp;#  This no longer works in certain locales and/or Linux distros.
  19&nbsp;#  POSIX is more portable.
  20&nbsp;#  Thanks to Frank Wang for pointing this out.
  21&nbsp;
  22&nbsp;#  Exercise:
  23&nbsp;#  --------
  24&nbsp;#  As the script stands, it accepts a single keystroke, then terminates.
  25&nbsp;#  Change the script so it accepts repeated input,
  26&nbsp;#+ reports on each keystroke, and terminates only when "X" is hit.
  27&nbsp;#  Hint: enclose everything in a "while" loop.
  28&nbsp;
  29&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="EX30"
></A
><P
><B
>Example 11-26. Creating menus using <I
CLASS="FIRSTTERM"
>case</I
></B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;
   3&nbsp;# Crude address database
   4&nbsp;
   5&nbsp;clear # Clear the screen.
   6&nbsp;
   7&nbsp;echo "          Contact List"
   8&nbsp;echo "          ------- ----"
   9&nbsp;echo "Choose one of the following persons:" 
  10&nbsp;echo
  11&nbsp;echo "[E]vans, Roland"
  12&nbsp;echo "[J]ones, Mildred"
  13&nbsp;echo "[S]mith, Julie"
  14&nbsp;echo "[Z]ane, Morris"
  15&nbsp;echo
  16&nbsp;
  17&nbsp;read person
  18&nbsp;
  19&nbsp;case "$person" in
  20&nbsp;# Note variable is quoted.
  21&nbsp;
  22&nbsp;  "E" | "e" )
  23&nbsp;  # Accept upper or lowercase input.
  24&nbsp;  echo
  25&nbsp;  echo "Roland Evans"
  26&nbsp;  echo "4321 Flash Dr."
  27&nbsp;  echo "Hardscrabble, CO 80753"
  28&nbsp;  echo "(303) 734-9874"
  29&nbsp;  echo "(303) 734-9892 fax"
  30&nbsp;  echo "revans@zzy.net"
  31&nbsp;  echo "Business partner &#38; old friend"
  32&nbsp;  ;;
  33&nbsp;# Note double semicolon to terminate each option.
  34&nbsp;
  35&nbsp;  "J" | "j" )
  36&nbsp;  echo
  37&nbsp;  echo "Mildred Jones"
  38&nbsp;  echo "249 E. 7th St., Apt. 19"
  39&nbsp;  echo "New York, NY 10009"
  40&nbsp;  echo "(212) 533-2814"
  41&nbsp;  echo "(212) 533-9972 fax"
  42&nbsp;  echo "milliej@loisaida.com"
  43&nbsp;  echo "Ex-girlfriend"
  44&nbsp;  echo "Birthday: Feb. 11"
  45&nbsp;  ;;
  46&nbsp;
  47&nbsp;# Add info for Smith &#38; Zane later.
  48&nbsp;
  49&nbsp;          * )
  50&nbsp;   # Default option.	  
  51&nbsp;   # Empty input (hitting RETURN) fits here, too.
  52&nbsp;   echo
  53&nbsp;   echo "Not yet in database."
  54&nbsp;  ;;
  55&nbsp;
  56&nbsp;esac
  57&nbsp;
  58&nbsp;echo
  59&nbsp;
  60&nbsp;#  Exercise:
  61&nbsp;#  --------
  62&nbsp;#  Change the script so it accepts multiple inputs,
  63&nbsp;#+ instead of terminating after displaying just one address.
  64&nbsp;
  65&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
><A
NAME="CASECL"
></A
></P
><P
>An exceptionally clever use of <B
CLASS="COMMAND"
>case</B
>
	      involves testing for command-line parameters.
	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#! /bin/bash
   2&nbsp;
   3&nbsp;case "$1" in
   4&nbsp;  "") echo "Usage: ${0##*/} &#60;filename&#62;"; exit $E_PARAM;;
   5&nbsp;                      # No command-line parameters,
   6&nbsp;                      # or first parameter empty.
   7&nbsp;# Note that ${0##*/} is ${var##pattern} param substitution.
   8&nbsp;                      # Net result is $0.
   9&nbsp;
  10&nbsp;  -*) FILENAME=./$1;;   #  If filename passed as argument ($1)
  11&nbsp;                      #+ starts with a dash,
  12&nbsp;                      #+ replace it with ./$1
  13&nbsp;                      #+ so further commands don't interpret it
  14&nbsp;                      #+ as an option.
  15&nbsp;
  16&nbsp;  * ) FILENAME=$1;;     # Otherwise, $1.
  17&nbsp;esac</PRE
></TD
></TR
></TABLE
></P
><P
>Here is a more straightforward example of
	      command-line parameter handling:
	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#! /bin/bash
   2&nbsp;
   3&nbsp;
   4&nbsp;while [ $# -gt 0 ]; do    # Until you run out of parameters . . .
   5&nbsp;  case "$1" in
   6&nbsp;    -d|--debug)
   7&nbsp;              # "-d" or "--debug" parameter?
   8&nbsp;              DEBUG=1
   9&nbsp;              ;;
  10&nbsp;    -c|--conf)
  11&nbsp;              CONFFILE="$2"
  12&nbsp;              shift
  13&nbsp;              if [ ! -f $CONFFILE ]; then
  14&nbsp;                echo "Error: Supplied file doesn't exist!"
  15&nbsp;                exit $E_CONFFILE     # File not found error.
  16&nbsp;              fi
  17&nbsp;              ;;
  18&nbsp;  esac
  19&nbsp;  shift       # Check next set of parameters.
  20&nbsp;done
  21&nbsp;
  22&nbsp;#  From Stefano Falsetto's "Log2Rot" script,
  23&nbsp;#+ part of his "rottlog" package.
  24&nbsp;#  Used with permission.</PRE
></TD
></TR
></TABLE
></P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="CASECMD"
></A
><P
><B
>Example 11-27. Using <I
CLASS="FIRSTTERM"
>command substitution</I
>
	      to generate the <I
CLASS="FIRSTTERM"
>case</I
> variable</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# case-cmd.sh: Using command substitution to generate a "case" variable.
   3&nbsp;
   4&nbsp;case $( arch ) in   # $( arch ) returns machine architecture.
   5&nbsp;                    # Equivalent to 'uname -m' ...
   6&nbsp;  i386 ) echo "80386-based machine";;
   7&nbsp;  i486 ) echo "80486-based machine";;
   8&nbsp;  i586 ) echo "Pentium-based machine";;
   9&nbsp;  i686 ) echo "Pentium2+-based machine";;
  10&nbsp;  *    ) echo "Other type of machine";;
  11&nbsp;esac
  12&nbsp;
  13&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
><A
NAME="CSGLOB"
></A
></P
><P
>A <B
CLASS="COMMAND"
>case</B
> construct can filter strings for
	      <A
HREF="globbingref.html"
>globbing</A
> patterns.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="MATCHSTRING"
></A
><P
><B
>Example 11-28. Simple string matching</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# match-string.sh: Simple string matching
   3&nbsp;#                  using a 'case' construct.
   4&nbsp;
   5&nbsp;match_string ()
   6&nbsp;{ # Exact string match.
   7&nbsp;  MATCH=0
   8&nbsp;  E_NOMATCH=90
   9&nbsp;  PARAMS=2     # Function requires 2 arguments.
  10&nbsp;  E_BAD_PARAMS=91
  11&nbsp;
  12&nbsp;  [ $# -eq $PARAMS ] || return $E_BAD_PARAMS
  13&nbsp;
  14&nbsp;  case "$1" in
  15&nbsp;  "$2") return $MATCH;;
  16&nbsp;  *   ) return $E_NOMATCH;;
  17&nbsp;  esac
  18&nbsp;
  19&nbsp;}  
  20&nbsp;
  21&nbsp;
  22&nbsp;a=one
  23&nbsp;b=two
  24&nbsp;c=three
  25&nbsp;d=two
  26&nbsp;
  27&nbsp;
  28&nbsp;match_string $a     # wrong number of parameters
  29&nbsp;echo $?             # 91
  30&nbsp;
  31&nbsp;match_string $a $b  # no match
  32&nbsp;echo $?             # 90
  33&nbsp;
  34&nbsp;match_string $b $d  # match
  35&nbsp;echo $?             # 0
  36&nbsp;
  37&nbsp;
  38&nbsp;exit 0		    </PRE
></TD
></TR
></TABLE
><HR></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="ISALPHA"
></A
><P
><B
>Example 11-29. Checking for alphabetic input</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# isalpha.sh: Using a "case" structure to filter a string.
   3&nbsp;
   4&nbsp;SUCCESS=0
   5&nbsp;FAILURE=1   #  Was FAILURE=-1,
   6&nbsp;            #+ but Bash no longer allows negative return value.
   7&nbsp;
   8&nbsp;isalpha ()  # Tests whether *first character* of input string is alphabetic.
   9&nbsp;{
  10&nbsp;if [ -z "$1" ]                # No argument passed?
  11&nbsp;then
  12&nbsp;  return $FAILURE
  13&nbsp;fi
  14&nbsp;
  15&nbsp;case "$1" in
  16&nbsp;  [a-zA-Z]*) return $SUCCESS;;  # Begins with a letter?
  17&nbsp;  *        ) return $FAILURE;;
  18&nbsp;esac
  19&nbsp;}             # Compare this with "isalpha ()" function in C.
  20&nbsp;
  21&nbsp;
  22&nbsp;isalpha2 ()   # Tests whether *entire string* is alphabetic.
  23&nbsp;{
  24&nbsp;  [ $# -eq 1 ] || return $FAILURE
  25&nbsp;
  26&nbsp;  case $1 in
  27&nbsp;  *[!a-zA-Z]*|"") return $FAILURE;;
  28&nbsp;               *) return $SUCCESS;;
  29&nbsp;  esac
  30&nbsp;}
  31&nbsp;
  32&nbsp;isdigit ()    # Tests whether *entire string* is numerical.
  33&nbsp;{             # In other words, tests for integer variable.
  34&nbsp;  [ $# -eq 1 ] || return $FAILURE
  35&nbsp;
  36&nbsp;  case $1 in
  37&nbsp;    *[!0-9]*|"") return $FAILURE;;
  38&nbsp;              *) return $SUCCESS;;
  39&nbsp;  esac
  40&nbsp;}
  41&nbsp;
  42&nbsp;
  43&nbsp;
  44&nbsp;check_var ()  # Front-end to isalpha ().
  45&nbsp;{
  46&nbsp;if isalpha "$@"
  47&nbsp;then
  48&nbsp;  echo "\"$*\" begins with an alpha character."
  49&nbsp;  if isalpha2 "$@"
  50&nbsp;  then        # No point in testing if first char is non-alpha.
  51&nbsp;    echo "\"$*\" contains only alpha characters."
  52&nbsp;  else
  53&nbsp;    echo "\"$*\" contains at least one non-alpha character."
  54&nbsp;  fi  
  55&nbsp;else
  56&nbsp;  echo "\"$*\" begins with a non-alpha character."
  57&nbsp;              # Also "non-alpha" if no argument passed.
  58&nbsp;fi
  59&nbsp;
  60&nbsp;echo
  61&nbsp;
  62&nbsp;}
  63&nbsp;
  64&nbsp;digit_check ()  # Front-end to isdigit ().
  65&nbsp;{
  66&nbsp;if isdigit "$@"
  67&nbsp;then
  68&nbsp;  echo "\"$*\" contains only digits [0 - 9]."
  69&nbsp;else
  70&nbsp;  echo "\"$*\" has at least one non-digit character."
  71&nbsp;fi
  72&nbsp;
  73&nbsp;echo
  74&nbsp;
  75&nbsp;}
  76&nbsp;
  77&nbsp;a=23skidoo
  78&nbsp;b=H3llo
  79&nbsp;c=-What?
  80&nbsp;d=What?
  81&nbsp;e=$(echo $b)   # Command substitution.
  82&nbsp;f=AbcDef
  83&nbsp;g=27234
  84&nbsp;h=27a34
  85&nbsp;i=27.34
  86&nbsp;
  87&nbsp;check_var $a
  88&nbsp;check_var $b
  89&nbsp;check_var $c
  90&nbsp;check_var $d
  91&nbsp;check_var $e
  92&nbsp;check_var $f
  93&nbsp;check_var     # No argument passed, so what happens?
  94&nbsp;#
  95&nbsp;digit_check $g
  96&nbsp;digit_check $h
  97&nbsp;digit_check $i
  98&nbsp;
  99&nbsp;
 100&nbsp;exit 0        # Script improved by S.C.
 101&nbsp;
 102&nbsp;# Exercise:
 103&nbsp;# --------
 104&nbsp;#  Write an 'isfloat ()' function that tests for floating point numbers.
 105&nbsp;#  Hint: The function duplicates 'isdigit ()',
 106&nbsp;#+ but adds a test for a mandatory decimal point.</PRE
></TD
></TR
></TABLE
><HR></DIV
></DD
><DT
><A
NAME="SELECTREF"
></A
><B
CLASS="COMMAND"
>select</B
></DT
><DD
><P
>The <B
CLASS="COMMAND"
>select</B
> construct, adopted from the Korn
	      Shell, is yet another tool for building menus.</P
><P
><P
><B
CLASS="COMMAND"
>select</B
>   <TT
CLASS="REPLACEABLE"
><I
>variable</I
></TT
>  [in <TT
CLASS="REPLACEABLE"
><I
>list</I
></TT
>]<BR>  do <BR>  <TT
CLASS="REPLACEABLE"
><I
>command</I
></TT
>... <BR>  break <BR>  done </P
></P
><P
>This prompts the user to enter one of the choices presented in the
	      variable list.  Note that <B
CLASS="COMMAND"
>select</B
> uses the
	      <TT
CLASS="VARNAME"
>$PS3</TT
> prompt (<TT
CLASS="PROMPT"
>#? </TT
>) by default, 
		but this may be changed.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="EX31"
></A
><P
><B
>Example 11-30. Creating menus using <I
CLASS="FIRSTTERM"
>select</I
></B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;
   3&nbsp;PS3='Choose your favorite vegetable: ' # Sets the prompt string.
   4&nbsp;                                       # Otherwise it defaults to #? .
   5&nbsp;
   6&nbsp;echo
   7&nbsp;
   8&nbsp;select vegetable in "beans" "carrots" "potatoes" "onions" "rutabagas"
   9&nbsp;do
  10&nbsp;  echo
  11&nbsp;  echo "Your favorite veggie is $vegetable."
  12&nbsp;  echo "Yuck!"
  13&nbsp;  echo
  14&nbsp;  break  # What happens if there is no 'break' here?
  15&nbsp;done
  16&nbsp;
  17&nbsp;exit
  18&nbsp;
  19&nbsp;# Exercise:
  20&nbsp;# --------
  21&nbsp;#  Fix this script to accept user input not specified in
  22&nbsp;#+ the "select" statement.
  23&nbsp;#  For example, if the user inputs "peas,"
  24&nbsp;#+ the script would respond "Sorry. That is not on the menu."</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
><A
NAME="INLISTOMIT"
></A
></P
><P
>If <TT
CLASS="USERINPUT"
><B
>in <TT
CLASS="REPLACEABLE"
><I
>list</I
></TT
></B
></TT
> is
	      omitted, then <B
CLASS="COMMAND"
>select</B
> uses the list of command
	      line arguments (<TT
CLASS="VARNAME"
>$@</TT
>) passed to the script or
	      the function containing the <B
CLASS="COMMAND"
>select</B
>
	      construct.</P
><P
>Compare this to the behavior of a 
	      <P
><B
CLASS="COMMAND"
>for</B
>   <TT
CLASS="REPLACEABLE"
><I
>variable</I
></TT
>  [in <TT
CLASS="REPLACEABLE"
><I
>list</I
></TT
>]</P
>
	      construct with the 
	      <TT
CLASS="USERINPUT"
><B
>in <TT
CLASS="REPLACEABLE"
><I
>list</I
></TT
></B
></TT
>
	      omitted.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="EX32"
></A
><P
><B
>Example 11-31. Creating menus using <I
CLASS="FIRSTTERM"
>select</I
>
	      in a function</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;
   3&nbsp;PS3='Choose your favorite vegetable: '
   4&nbsp;
   5&nbsp;echo
   6&nbsp;
   7&nbsp;choice_of()
   8&nbsp;{
   9&nbsp;select vegetable
  10&nbsp;# [in list] omitted, so 'select' uses arguments passed to function.
  11&nbsp;do
  12&nbsp;  echo
  13&nbsp;  echo "Your favorite veggie is $vegetable."
  14&nbsp;  echo "Yuck!"
  15&nbsp;  echo
  16&nbsp;  break
  17&nbsp;done
  18&nbsp;}
  19&nbsp;
  20&nbsp;choice_of beans rice carrots radishes rutabaga spinach
  21&nbsp;#         $1    $2   $3      $4       $5       $6
  22&nbsp;#         passed to choice_of() function
  23&nbsp;
  24&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
>See also <A
HREF="bash2.html#RESISTOR"
>Example 37-3</A
>.</P
></DD
></DL
></DIV
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
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><TD
ALIGN="LEFT"
VALIGN="TOP"
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><A
NAME="FTN.AEN7087"
HREF="testbranch.html#AEN7087"
>[1]</A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>Pattern-match lines may also <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>start</I
></SPAN
>
    with a <B
CLASS="COMMAND"
>(</B
> left paren to give the layout
    a more structured appearance.</P
><P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;case $( arch ) in   # $( arch ) returns machine architecture.
   2&nbsp;  ( i386 ) echo "80386-based machine";;
   3&nbsp;# ^      ^
   4&nbsp;  ( i486 ) echo "80486-based machine";;
   5&nbsp;  ( i586 ) echo "Pentium-based machine";;
   6&nbsp;  ( i686 ) echo "Pentium2+-based machine";;
   7&nbsp;  (    * ) echo "Other type of machine";;
   8&nbsp;esac</PRE
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