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>Advanced Bash-Scripting Guide: An in-depth exploration of the art of shell scripting</TH
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>Chapter 36. Miscellany</TD
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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="COLORIZING"
></A
>36.5. <SPAN
CLASS="QUOTE"
>"Colorizing"</SPAN
> Scripts</H1
><P
><A
NAME="COLORIZINGREF"
></A
></P
><P
>The ANSI
	   <A
NAME="AEN20259"
HREF="#FTN.AEN20259"
>[1]</A
>
	   escape sequences set screen attributes, such as bold
	   text, and color of foreground and background. <A
HREF="dosbatch.html#DOSBATCH1"
>DOS batch files</A
> commonly used
	   ANSI escape codes for <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>color</I
></SPAN
> output,
	   and so can Bash scripts.</P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="EX30A"
></A
><P
><B
>Example 36-13. A <SPAN
CLASS="QUOTE"
>"colorized"</SPAN
> address database</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# ex30a.sh: "Colorized" version of ex30.sh.
   3&nbsp;#            Crude address database
   4&nbsp;
   5&nbsp;
   6&nbsp;clear                                   # Clear the screen.
   7&nbsp;
   8&nbsp;echo -n "          "
   9&nbsp;echo -e '\E[37;44m'"\033[1mContact List\033[0m"
  10&nbsp;                                        # White on blue background
  11&nbsp;echo; echo
  12&nbsp;echo -e "\033[1mChoose one of the following persons:\033[0m"
  13&nbsp;                                        # Bold
  14&nbsp;tput sgr0                               # Reset attributes.
  15&nbsp;echo "(Enter only the first letter of name.)"
  16&nbsp;echo
  17&nbsp;echo -en '\E[47;34m'"\033[1mE\033[0m"   # Blue
  18&nbsp;tput sgr0                               # Reset colors to "normal."
  19&nbsp;echo "vans, Roland"                     # "[E]vans, Roland"
  20&nbsp;echo -en '\E[47;35m'"\033[1mJ\033[0m"   # Magenta
  21&nbsp;tput sgr0
  22&nbsp;echo "ambalaya, Mildred"
  23&nbsp;echo -en '\E[47;32m'"\033[1mS\033[0m"   # Green
  24&nbsp;tput sgr0
  25&nbsp;echo "mith, Julie"
  26&nbsp;echo -en '\E[47;31m'"\033[1mZ\033[0m"   # Red
  27&nbsp;tput sgr0
  28&nbsp;echo "ane, Morris"
  29&nbsp;echo
  30&nbsp;
  31&nbsp;read person
  32&nbsp;
  33&nbsp;case "$person" in
  34&nbsp;# Note variable is quoted.
  35&nbsp;
  36&nbsp;  "E" | "e" )
  37&nbsp;  # Accept upper or lowercase input.
  38&nbsp;  echo
  39&nbsp;  echo "Roland Evans"
  40&nbsp;  echo "4321 Flash Dr."
  41&nbsp;  echo "Hardscrabble, CO 80753"
  42&nbsp;  echo "(303) 734-9874"
  43&nbsp;  echo "(303) 734-9892 fax"
  44&nbsp;  echo "revans@zzy.net"
  45&nbsp;  echo "Business partner &#38; old friend"
  46&nbsp;  ;;
  47&nbsp;
  48&nbsp;  "J" | "j" )
  49&nbsp;  echo
  50&nbsp;  echo "Mildred Jambalaya"
  51&nbsp;  echo "249 E. 7th St., Apt. 19"
  52&nbsp;  echo "New York, NY 10009"
  53&nbsp;  echo "(212) 533-2814"
  54&nbsp;  echo "(212) 533-9972 fax"
  55&nbsp;  echo "milliej@loisaida.com"
  56&nbsp;  echo "Girlfriend"
  57&nbsp;  echo "Birthday: Feb. 11"
  58&nbsp;  ;;
  59&nbsp;
  60&nbsp;# Add info for Smith &#38; Zane later.
  61&nbsp;
  62&nbsp;          * )
  63&nbsp;   # Default option.	  
  64&nbsp;   # Empty input (hitting RETURN) fits here, too.
  65&nbsp;   echo
  66&nbsp;   echo "Not yet in database."
  67&nbsp;  ;;
  68&nbsp;
  69&nbsp;esac
  70&nbsp;
  71&nbsp;tput sgr0                               # Reset colors to "normal."
  72&nbsp;
  73&nbsp;echo
  74&nbsp;
  75&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="DRAW-BOX"
></A
><P
><B
>Example 36-14. Drawing a box</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# Draw-box.sh: Drawing a box using ASCII characters.
   3&nbsp;
   4&nbsp;# Script by Stefano Palmeri, with minor editing by document author.
   5&nbsp;# Minor edits suggested by Jim Angstadt.
   6&nbsp;# Used in the ABS Guide with permission.
   7&nbsp;
   8&nbsp;
   9&nbsp;######################################################################
  10&nbsp;###  draw_box function doc  ###
  11&nbsp;
  12&nbsp;#  The "draw_box" function lets the user
  13&nbsp;#+ draw a box in a terminal.       
  14&nbsp;#
  15&nbsp;#  Usage: draw_box ROW COLUMN HEIGHT WIDTH [COLOR] 
  16&nbsp;#  ROW and COLUMN represent the position        
  17&nbsp;#+ of the upper left angle of the box you're going to draw.
  18&nbsp;#  ROW and COLUMN must be greater than 0
  19&nbsp;#+ and less than current terminal dimension.
  20&nbsp;#  HEIGHT is the number of rows of the box, and must be &#62; 0. 
  21&nbsp;#  HEIGHT + ROW must be &#60;= than current terminal height. 
  22&nbsp;#  WIDTH is the number of columns of the box and must be &#62; 0.
  23&nbsp;#  WIDTH + COLUMN must be &#60;= than current terminal width.
  24&nbsp;#
  25&nbsp;# E.g.: If your terminal dimension is 20x80,
  26&nbsp;#  draw_box 2 3 10 45 is good
  27&nbsp;#  draw_box 2 3 19 45 has bad HEIGHT value (19+2 &#62; 20)
  28&nbsp;#  draw_box 2 3 18 78 has bad WIDTH value (78+3 &#62; 80)
  29&nbsp;#
  30&nbsp;#  COLOR is the color of the box frame.
  31&nbsp;#  This is the 5th argument and is optional.
  32&nbsp;#  0=black 1=red 2=green 3=tan 4=blue 5=purple 6=cyan 7=white.
  33&nbsp;#  If you pass the function bad arguments,
  34&nbsp;#+ it will just exit with code 65,
  35&nbsp;#+ and no messages will be printed on stderr.
  36&nbsp;#
  37&nbsp;#  Clear the terminal before you start to draw a box.
  38&nbsp;#  The clear command is not contained within the function.
  39&nbsp;#  This allows the user to draw multiple boxes, even overlapping ones.
  40&nbsp;
  41&nbsp;###  end of draw_box function doc  ### 
  42&nbsp;######################################################################
  43&nbsp;
  44&nbsp;draw_box(){
  45&nbsp;
  46&nbsp;#=============#
  47&nbsp;HORZ="-"
  48&nbsp;VERT="|"
  49&nbsp;CORNER_CHAR="+"
  50&nbsp;
  51&nbsp;MINARGS=4
  52&nbsp;E_BADARGS=65
  53&nbsp;#=============#
  54&nbsp;
  55&nbsp;
  56&nbsp;if [ $# -lt "$MINARGS" ]; then          # If args are less than 4, exit.
  57&nbsp;    exit $E_BADARGS
  58&nbsp;fi
  59&nbsp;
  60&nbsp;# Looking for non digit chars in arguments.
  61&nbsp;# Probably it could be done better (exercise for the reader?).
  62&nbsp;if echo $@ | tr -d [:blank:] | tr -d [:digit:] | grep . &#38;&#62; /dev/null; then
  63&nbsp;   exit $E_BADARGS
  64&nbsp;fi
  65&nbsp;
  66&nbsp;BOX_HEIGHT=`expr $3 - 1`   #  -1 correction needed because angle char "+"
  67&nbsp;BOX_WIDTH=`expr $4 - 1`    #+ is a part of both box height and width.
  68&nbsp;T_ROWS=`tput lines`        #  Define current terminal dimension 
  69&nbsp;T_COLS=`tput cols`         #+ in rows and columns.
  70&nbsp;         
  71&nbsp;if [ $1 -lt 1 ] || [ $1 -gt $T_ROWS ]; then    #  Start checking if arguments
  72&nbsp;   exit $E_BADARGS                             #+ are correct.
  73&nbsp;fi
  74&nbsp;if [ $2 -lt 1 ] || [ $2 -gt $T_COLS ]; then
  75&nbsp;   exit $E_BADARGS
  76&nbsp;fi
  77&nbsp;if [ `expr $1 + $BOX_HEIGHT + 1` -gt $T_ROWS ]; then
  78&nbsp;   exit $E_BADARGS
  79&nbsp;fi
  80&nbsp;if [ `expr $2 + $BOX_WIDTH + 1` -gt $T_COLS ]; then
  81&nbsp;   exit $E_BADARGS
  82&nbsp;fi
  83&nbsp;if [ $3 -lt 1 ] || [ $4 -lt 1 ]; then
  84&nbsp;   exit $E_BADARGS
  85&nbsp;fi                                 # End checking arguments.
  86&nbsp;
  87&nbsp;plot_char(){                       # Function within a function.
  88&nbsp;   echo -e "\E[${1};${2}H"$3
  89&nbsp;}
  90&nbsp;
  91&nbsp;echo -ne "\E[3${5}m"               # Set box frame color, if defined.
  92&nbsp;
  93&nbsp;# start drawing the box
  94&nbsp;
  95&nbsp;count=1                                         #  Draw vertical lines using
  96&nbsp;for (( r=$1; count&#60;=$BOX_HEIGHT; r++)); do      #+ plot_char function.
  97&nbsp;  plot_char $r $2 $VERT
  98&nbsp;  let count=count+1
  99&nbsp;done 
 100&nbsp;
 101&nbsp;count=1
 102&nbsp;c=`expr $2 + $BOX_WIDTH`
 103&nbsp;for (( r=$1; count&#60;=$BOX_HEIGHT; r++)); do
 104&nbsp;  plot_char $r $c $VERT
 105&nbsp;  let count=count+1
 106&nbsp;done 
 107&nbsp;
 108&nbsp;count=1                                        #  Draw horizontal lines using
 109&nbsp;for (( c=$2; count&#60;=$BOX_WIDTH; c++)); do      #+ plot_char function.
 110&nbsp;  plot_char $1 $c $HORZ
 111&nbsp;  let count=count+1
 112&nbsp;done 
 113&nbsp;
 114&nbsp;count=1
 115&nbsp;r=`expr $1 + $BOX_HEIGHT`
 116&nbsp;for (( c=$2; count&#60;=$BOX_WIDTH; c++)); do
 117&nbsp;  plot_char $r $c $HORZ
 118&nbsp;  let count=count+1
 119&nbsp;done 
 120&nbsp;
 121&nbsp;plot_char $1 $2 $CORNER_CHAR                   # Draw box angles.
 122&nbsp;plot_char $1 `expr $2 + $BOX_WIDTH` $CORNER_CHAR
 123&nbsp;plot_char `expr $1 + $BOX_HEIGHT` $2 $CORNER_CHAR
 124&nbsp;plot_char `expr $1 + $BOX_HEIGHT` `expr $2 + $BOX_WIDTH` $CORNER_CHAR
 125&nbsp;
 126&nbsp;echo -ne "\E[0m"             #  Restore old colors.
 127&nbsp;
 128&nbsp;P_ROWS=`expr $T_ROWS - 1`    #  Put the prompt at bottom of the terminal.
 129&nbsp;
 130&nbsp;echo -e "\E[${P_ROWS};1H"
 131&nbsp;}      
 132&nbsp;
 133&nbsp;
 134&nbsp;# Now, let's try drawing a box.
 135&nbsp;clear                       # Clear the terminal.
 136&nbsp;R=2      # Row
 137&nbsp;C=3      # Column
 138&nbsp;H=10     # Height
 139&nbsp;W=45     # Width 
 140&nbsp;col=1    # Color (red)
 141&nbsp;draw_box $R $C $H $W $col   # Draw the box.
 142&nbsp;
 143&nbsp;exit 0
 144&nbsp;
 145&nbsp;# Exercise:
 146&nbsp;# --------
 147&nbsp;# Add the option of printing text within the drawn box.</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
>The simplest, and perhaps most useful ANSI escape sequence is
	  bold text, <B
CLASS="COMMAND"
>\033[1m ... \033[0m</B
>. The
	  <SPAN
CLASS="TOKEN"
>\033</SPAN
> represents an <A
HREF="escapingsection.html#ESCP"
>escape</A
>, the <SPAN
CLASS="QUOTE"
>"[1"</SPAN
> turns on the
	  bold attribute, while the <SPAN
CLASS="QUOTE"
>"[0"</SPAN
> switches it off. The
	  <SPAN
CLASS="QUOTE"
>"m"</SPAN
> terminates each term of the escape sequence.
	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>echo -e "\033[1mThis is bold text.\033[0m"</B
></TT
>
 	      </PRE
></TD
></TR
></TABLE
>
	</P
><P
>A similar escape sequence switches on the underline
	  attribute (on an <I
CLASS="FIRSTTERM"
>rxvt</I
> and an
	  <I
CLASS="FIRSTTERM"
>aterm</I
>).
	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>echo -e "\033[4mThis is underlined text.\033[0m"</B
></TT
>
 	      </PRE
></TD
></TR
></TABLE
>
	</P
><DIV
CLASS="NOTE"
><TABLE
CLASS="NOTE"
WIDTH="100%"
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
>With an <B
CLASS="COMMAND"
>echo</B
>, the
	  <TT
CLASS="OPTION"
>-e</TT
> option enables the escape
	  sequences.</P
></TD
></TR
></TABLE
></DIV
><P
>Other escape sequences change the text and/or background
	  color.</P
><P
>	      <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>echo -e '\E[34;47mThis prints in blue.'; tput sgr0</B
></TT
>
 
 
 <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>echo -e '\E[33;44m'"yellow text on blue background"; tput sgr0</B
></TT
>
 
 
 <TT
CLASS="PROMPT"
>bash$ </TT
><TT
CLASS="USERINPUT"
><B
>echo -e '\E[1;33;44m'"BOLD yellow text on blue background"; tput sgr0</B
></TT
>
 	      </PRE
></TD
></TR
></TABLE
>
	      </P
><DIV
CLASS="NOTE"
><TABLE
CLASS="NOTE"
WIDTH="100%"
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
>It's usually advisable to set the
	  <I
CLASS="FIRSTTERM"
>bold</I
> attribute for light-colored foreground
	  text.</P
></TD
></TR
></TABLE
></DIV
><P
>The <B
CLASS="COMMAND"
>tput sgr0</B
> restores the
		terminal settings to normal. Omitting this lets all
	        subsequent output from that particular terminal remain
	        blue.</P
><DIV
CLASS="NOTE"
><TABLE
CLASS="NOTE"
WIDTH="100%"
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
>Since <B
CLASS="COMMAND"
>tput sgr0</B
> fails to restore
	        terminal settings under certain circumstances,
		<B
CLASS="COMMAND"
>echo -ne \E[0m</B
> may be a better choice.</P
></TD
></TR
></TABLE
></DIV
><P
><A
NAME="COLORIZTEMPL"
></A
></P
><TABLE
CLASS="SIDEBAR"
BORDER="1"
CELLPADDING="5"
><TR
><TD
><DIV
CLASS="SIDEBAR"
><A
NAME="AEN20311"
></A
><P
>Use the following template for writing colored text on a colored
	background.</P
><P
>	  <TT
CLASS="USERINPUT"
><B
>echo -e '\E[COLOR1;COLOR2mSome text goes here.'</B
></TT
>
        </P
><P
>The <SPAN
CLASS="QUOTE"
>"\E["</SPAN
> begins the escape sequence.
	  The semicolon-separated numbers <SPAN
CLASS="QUOTE"
>"COLOR1"</SPAN
> and
	  <SPAN
CLASS="QUOTE"
>"COLOR2"</SPAN
> specify a foreground and a background
	  color, according to the table below. (The order of the
	  numbers does not matter, since the foreground and background
	  numbers fall in non-overlapping ranges.) The <SPAN
CLASS="QUOTE"
>"m"</SPAN
>
	  terminates the escape sequence, and the text begins immediately
	  after that.</P
><P
>Note also that <A
HREF="variables.html#SNGLQUO"
>single quotes</A
>
	  enclose the remainder of the command sequence following the
	  <B
CLASS="COMMAND"
>echo -e</B
>.</P
></DIV
></TD
></TR
></TABLE
><P
>The numbers in the following table work for an
	  <I
CLASS="FIRSTTERM"
>rxvt</I
> terminal. Results may vary for other
	  terminal emulators.</P
><P
><A
NAME="COLORIZTABLE"
></A
></P
><DIV
CLASS="TABLE"
><HR><A
NAME="AEN20327"
></A
><P
><B
>Table 36-1. Numbers representing colors in Escape Sequences</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Color</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Foreground</TH
><TH
ALIGN="LEFT"
VALIGN="TOP"
>Background</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>black</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>30</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>40</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>red</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>31</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>41</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>green</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>32</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>42</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>yellow</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>33</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>43</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>blue</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>34</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>44</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>magenta</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>35</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>45</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>cyan</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>36</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>46</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>white</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>37</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>47</TD
></TR
></TBODY
></TABLE
><HR></DIV
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="COLORECHO"
></A
><P
><B
>Example 36-15. Echoing colored text</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# color-echo.sh: Echoing text messages in color.
   3&nbsp;
   4&nbsp;# Modify this script for your own purposes.
   5&nbsp;# It's easier than hand-coding color.
   6&nbsp;
   7&nbsp;black='\E[30;47m'
   8&nbsp;red='\E[31;47m'
   9&nbsp;green='\E[32;47m'
  10&nbsp;yellow='\E[33;47m'
  11&nbsp;blue='\E[34;47m'
  12&nbsp;magenta='\E[35;47m'
  13&nbsp;cyan='\E[36;47m'
  14&nbsp;white='\E[37;47m'
  15&nbsp;
  16&nbsp;
  17&nbsp;alias Reset="tput sgr0"      #  Reset text attributes to normal
  18&nbsp;                             #+ without clearing screen.
  19&nbsp;
  20&nbsp;
  21&nbsp;cecho ()                     # Color-echo.
  22&nbsp;                             # Argument $1 = message
  23&nbsp;                             # Argument $2 = color
  24&nbsp;{
  25&nbsp;local default_msg="No message passed."
  26&nbsp;                             # Doesn't really need to be a local variable.
  27&nbsp;
  28&nbsp;message=${1:-$default_msg}   # Defaults to default message.
  29&nbsp;color=${2:-$black}           # Defaults to black, if not specified.
  30&nbsp;
  31&nbsp;  echo -e "$color"
  32&nbsp;  echo "$message"
  33&nbsp;  Reset                      # Reset to normal.
  34&nbsp;
  35&nbsp;  return
  36&nbsp;}  
  37&nbsp;
  38&nbsp;
  39&nbsp;# Now, let's try it out.
  40&nbsp;# ----------------------------------------------------
  41&nbsp;cecho "Feeling blue..." $blue
  42&nbsp;cecho "Magenta looks more like purple." $magenta
  43&nbsp;cecho "Green with envy." $green
  44&nbsp;cecho "Seeing red?" $red
  45&nbsp;cecho "Cyan, more familiarly known as aqua." $cyan
  46&nbsp;cecho "No color passed (defaults to black)."
  47&nbsp;       # Missing $color argument.
  48&nbsp;cecho "\"Empty\" color passed (defaults to black)." ""
  49&nbsp;       # Empty $color argument.
  50&nbsp;cecho
  51&nbsp;       # Missing $message and $color arguments.
  52&nbsp;cecho "" ""
  53&nbsp;       # Empty $message and $color arguments.
  54&nbsp;# ----------------------------------------------------
  55&nbsp;
  56&nbsp;echo
  57&nbsp;
  58&nbsp;exit 0
  59&nbsp;
  60&nbsp;# Exercises:
  61&nbsp;# ---------
  62&nbsp;# 1) Add the "bold" attribute to the 'cecho ()' function.
  63&nbsp;# 2) Add options for colored backgrounds.</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
><A
NAME="HORSERACEREF"
></A
></P
><DIV
CLASS="EXAMPLE"
><HR><A
NAME="HORSERACE"
></A
><P
><B
>Example 36-16. A <SPAN
CLASS="QUOTE"
>"horserace"</SPAN
> game</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;#!/bin/bash
   2&nbsp;# horserace.sh: Very simple horserace simulation.
   3&nbsp;# Author: Stefano Palmeri
   4&nbsp;# Used with permission.
   5&nbsp;
   6&nbsp;################################################################
   7&nbsp;#  Goals of the script:
   8&nbsp;#  playing with escape sequences and terminal colors.
   9&nbsp;#
  10&nbsp;#  Exercise:
  11&nbsp;#  Edit the script to make it run less randomly,
  12&nbsp;#+ set up a fake betting shop . . .     
  13&nbsp;#  Um . . . um . . . it's starting to remind me of a movie . . .
  14&nbsp;#
  15&nbsp;#  The script gives each horse a random handicap.
  16&nbsp;#  The odds are calculated upon horse handicap
  17&nbsp;#+ and are expressed in European(?) style.
  18&nbsp;#  E.g., odds=3.75 means that if you bet $1 and win,
  19&nbsp;#+ you receive $3.75.
  20&nbsp;# 
  21&nbsp;#  The script has been tested with a GNU/Linux OS,
  22&nbsp;#+ using xterm and rxvt, and konsole.
  23&nbsp;#  On a machine with an AMD 900 MHz processor,
  24&nbsp;#+ the average race time is 75 seconds.    
  25&nbsp;#  On faster computers the race time would be lower.
  26&nbsp;#  So, if you want more suspense, reset the USLEEP_ARG variable.
  27&nbsp;#
  28&nbsp;#  Script by Stefano Palmeri.
  29&nbsp;################################################################
  30&nbsp;
  31&nbsp;E_RUNERR=65
  32&nbsp;
  33&nbsp;# Check if md5sum and bc are installed. 
  34&nbsp;if ! which bc &#38;&#62; /dev/null; then
  35&nbsp;   echo bc is not installed.  
  36&nbsp;   echo "Can\'t run . . . "
  37&nbsp;   exit $E_RUNERR
  38&nbsp;fi
  39&nbsp;if ! which md5sum &#38;&#62; /dev/null; then
  40&nbsp;   echo md5sum is not installed.  
  41&nbsp;   echo "Can\'t run . . . "
  42&nbsp;   exit $E_RUNERR
  43&nbsp;fi
  44&nbsp;
  45&nbsp;#  Set the following variable to slow down script execution.
  46&nbsp;#  It will be passed as the argument for usleep (man usleep)  
  47&nbsp;#+ and is expressed in microseconds (500000 = half a second).
  48&nbsp;USLEEP_ARG=0  
  49&nbsp;
  50&nbsp;#  Clean up the temp directory, restore terminal cursor and 
  51&nbsp;#+ terminal colors -- if script interrupted by Ctl-C.
  52&nbsp;trap 'echo -en "\E[?25h"; echo -en "\E[0m"; stty echo;\
  53&nbsp;tput cup 20 0; rm -fr  $HORSE_RACE_TMP_DIR'  TERM EXIT
  54&nbsp;#  See the chapter on debugging for an explanation of 'trap.'
  55&nbsp;
  56&nbsp;# Set a unique (paranoid) name for the temp directory the script needs.
  57&nbsp;HORSE_RACE_TMP_DIR=$HOME/.horserace-`date +%s`-`head -c10 /dev/urandom \
  58&nbsp;| md5sum | head -c30`
  59&nbsp;
  60&nbsp;# Create the temp directory and move right in.
  61&nbsp;mkdir $HORSE_RACE_TMP_DIR
  62&nbsp;cd $HORSE_RACE_TMP_DIR
  63&nbsp;
  64&nbsp;
  65&nbsp;#  This function moves the cursor to line $1 column $2 and then prints $3.
  66&nbsp;#  E.g.: "move_and_echo 5 10 linux" is equivalent to
  67&nbsp;#+ "tput cup 4 9; echo linux", but with one command instead of two.
  68&nbsp;#  Note: "tput cup" defines 0 0 the upper left angle of the terminal,
  69&nbsp;#+ echo defines 1 1 the upper left angle of the terminal.
  70&nbsp;move_and_echo() {
  71&nbsp;          echo -ne "\E[${1};${2}H""$3" 
  72&nbsp;}
  73&nbsp;
  74&nbsp;# Function to generate a pseudo-random number between 1 and 9. 
  75&nbsp;random_1_9 ()
  76&nbsp;{
  77&nbsp;    head -c10 /dev/urandom | md5sum | tr -d [a-z] | tr -d 0 | cut -c1 
  78&nbsp;}
  79&nbsp;
  80&nbsp;#  Two functions that simulate "movement," when drawing the horses. 
  81&nbsp;draw_horse_one() {
  82&nbsp;               echo -n " "//$MOVE_HORSE//
  83&nbsp;}
  84&nbsp;draw_horse_two(){
  85&nbsp;              echo -n " "\\\\$MOVE_HORSE\\\\ 
  86&nbsp;}   
  87&nbsp;
  88&nbsp;
  89&nbsp;# Define current terminal dimension.
  90&nbsp;N_COLS=`tput cols`
  91&nbsp;N_LINES=`tput lines`
  92&nbsp;
  93&nbsp;# Need at least a 20-LINES X 80-COLUMNS terminal. Check it.
  94&nbsp;if [ $N_COLS -lt 80 ] || [ $N_LINES -lt 20 ]; then
  95&nbsp;   echo "`basename $0` needs a 80-cols X 20-lines terminal."
  96&nbsp;   echo "Your terminal is ${N_COLS}-cols X ${N_LINES}-lines."
  97&nbsp;   exit $E_RUNERR
  98&nbsp;fi
  99&nbsp;
 100&nbsp;
 101&nbsp;# Start drawing the race field.
 102&nbsp;
 103&nbsp;# Need a string of 80 chars. See below.
 104&nbsp;BLANK80=`seq -s "" 100 | head -c80`
 105&nbsp;
 106&nbsp;clear
 107&nbsp;
 108&nbsp;# Set foreground and background colors to white.
 109&nbsp;echo -ne '\E[37;47m'
 110&nbsp;
 111&nbsp;# Move the cursor on the upper left angle of the terminal.
 112&nbsp;tput cup 0 0 
 113&nbsp;
 114&nbsp;# Draw six white lines.
 115&nbsp;for n in `seq 5`; do
 116&nbsp;      echo $BLANK80   # Use the 80 chars string to colorize the terminal.
 117&nbsp;done
 118&nbsp;
 119&nbsp;# Sets foreground color to black. 
 120&nbsp;echo -ne '\E[30m'
 121&nbsp;
 122&nbsp;move_and_echo 3 1 "START  1"            
 123&nbsp;move_and_echo 3 75 FINISH
 124&nbsp;move_and_echo 1 5 "|"
 125&nbsp;move_and_echo 1 80 "|"
 126&nbsp;move_and_echo 2 5 "|"
 127&nbsp;move_and_echo 2 80 "|"
 128&nbsp;move_and_echo 4 5 "|  2"
 129&nbsp;move_and_echo 4 80 "|"
 130&nbsp;move_and_echo 5 5 "V  3"
 131&nbsp;move_and_echo 5 80 "V"
 132&nbsp;
 133&nbsp;# Set foreground color to red. 
 134&nbsp;echo -ne '\E[31m'
 135&nbsp;
 136&nbsp;# Some ASCII art.
 137&nbsp;move_and_echo 1 8 "..@@@..@@@@@...@@@@@.@...@..@@@@..."
 138&nbsp;move_and_echo 2 8 ".@...@...@.......@...@...@.@......."
 139&nbsp;move_and_echo 3 8 ".@@@@@...@.......@...@@@@@.@@@@...."
 140&nbsp;move_and_echo 4 8 ".@...@...@.......@...@...@.@......."
 141&nbsp;move_and_echo 5 8 ".@...@...@.......@...@...@..@@@@..."
 142&nbsp;move_and_echo 1 43 "@@@@...@@@...@@@@..@@@@..@@@@."
 143&nbsp;move_and_echo 2 43 "@...@.@...@.@.....@.....@....."
 144&nbsp;move_and_echo 3 43 "@@@@..@@@@@.@.....@@@@...@@@.."
 145&nbsp;move_and_echo 4 43 "@..@..@...@.@.....@.........@."
 146&nbsp;move_and_echo 5 43 "@...@.@...@..@@@@..@@@@.@@@@.."
 147&nbsp;
 148&nbsp;
 149&nbsp;# Set foreground and background colors to green.
 150&nbsp;echo -ne '\E[32;42m'
 151&nbsp;
 152&nbsp;# Draw  eleven green lines.
 153&nbsp;tput cup 5 0
 154&nbsp;for n in `seq 11`; do
 155&nbsp;      echo $BLANK80
 156&nbsp;done
 157&nbsp;
 158&nbsp;# Set foreground color to black. 
 159&nbsp;echo -ne '\E[30m'
 160&nbsp;tput cup 5 0
 161&nbsp;
 162&nbsp;# Draw the fences. 
 163&nbsp;echo "++++++++++++++++++++++++++++++++++++++\
 164&nbsp;++++++++++++++++++++++++++++++++++++++++++"
 165&nbsp;
 166&nbsp;tput cup 15 0
 167&nbsp;echo "++++++++++++++++++++++++++++++++++++++\
 168&nbsp;++++++++++++++++++++++++++++++++++++++++++"
 169&nbsp;
 170&nbsp;# Set foreground and background colors to white.
 171&nbsp;echo -ne '\E[37;47m'
 172&nbsp;
 173&nbsp;# Draw three white lines.
 174&nbsp;for n in `seq 3`; do
 175&nbsp;      echo $BLANK80
 176&nbsp;done
 177&nbsp;
 178&nbsp;# Set foreground color to black.
 179&nbsp;echo -ne '\E[30m'
 180&nbsp;
 181&nbsp;# Create 9 files to stores handicaps.
 182&nbsp;for n in `seq 10 7 68`; do
 183&nbsp;      touch $n
 184&nbsp;done  
 185&nbsp;
 186&nbsp;# Set the first type of "horse" the script will draw.
 187&nbsp;HORSE_TYPE=2
 188&nbsp;
 189&nbsp;#  Create position-file and odds-file for every "horse".
 190&nbsp;#+ In these files, store the current position of the horse,
 191&nbsp;#+ the type and the odds.
 192&nbsp;for HN in `seq 9`; do
 193&nbsp;      touch horse_${HN}_position
 194&nbsp;      touch odds_${HN}
 195&nbsp;      echo \-1 &#62; horse_${HN}_position
 196&nbsp;      echo $HORSE_TYPE &#62;&#62;  horse_${HN}_position
 197&nbsp;      # Define a random handicap for horse.
 198&nbsp;       HANDICAP=`random_1_9`
 199&nbsp;      # Check if the random_1_9 function returned a good value.
 200&nbsp;      while ! echo $HANDICAP | grep [1-9] &#38;&#62; /dev/null; do
 201&nbsp;                HANDICAP=`random_1_9`
 202&nbsp;      done
 203&nbsp;      # Define last handicap position for horse. 
 204&nbsp;      LHP=`expr $HANDICAP \* 7 + 3`
 205&nbsp;      for FILE in `seq 10 7 $LHP`; do
 206&nbsp;            echo $HN &#62;&#62; $FILE
 207&nbsp;      done   
 208&nbsp;     
 209&nbsp;      # Calculate odds.
 210&nbsp;      case $HANDICAP in 
 211&nbsp;              1) ODDS=`echo $HANDICAP \* 0.25 + 1.25 | bc`
 212&nbsp;                                 echo $ODDS &#62; odds_${HN}
 213&nbsp;              ;;
 214&nbsp;              2 | 3) ODDS=`echo $HANDICAP \* 0.40 + 1.25 | bc`
 215&nbsp;                                       echo $ODDS &#62; odds_${HN}
 216&nbsp;              ;;
 217&nbsp;              4 | 5 | 6) ODDS=`echo $HANDICAP \* 0.55 + 1.25 | bc`
 218&nbsp;                                             echo $ODDS &#62; odds_${HN}
 219&nbsp;              ;; 
 220&nbsp;              7 | 8) ODDS=`echo $HANDICAP \* 0.75 + 1.25 | bc`
 221&nbsp;                                       echo $ODDS &#62; odds_${HN}
 222&nbsp;              ;; 
 223&nbsp;              9) ODDS=`echo $HANDICAP \* 0.90 + 1.25 | bc`
 224&nbsp;                                  echo $ODDS &#62; odds_${HN}
 225&nbsp;      esac
 226&nbsp;
 227&nbsp;
 228&nbsp;done
 229&nbsp;
 230&nbsp;
 231&nbsp;# Print odds.
 232&nbsp;print_odds() {
 233&nbsp;tput cup 6 0
 234&nbsp;echo -ne '\E[30;42m'
 235&nbsp;for HN in `seq 9`; do
 236&nbsp;      echo "#$HN odds-&#62;" `cat odds_${HN}`
 237&nbsp;done
 238&nbsp;}
 239&nbsp;
 240&nbsp;# Draw the horses at starting line.
 241&nbsp;draw_horses() {
 242&nbsp;tput cup 6 0
 243&nbsp;echo -ne '\E[30;42m'
 244&nbsp;for HN in `seq 9`; do
 245&nbsp;      echo /\\$HN/\\"                               "
 246&nbsp;done
 247&nbsp;}
 248&nbsp;
 249&nbsp;print_odds
 250&nbsp;
 251&nbsp;echo -ne '\E[47m'
 252&nbsp;# Wait for a enter key press to start the race.
 253&nbsp;# The escape sequence '\E[?25l' disables the cursor.
 254&nbsp;tput cup 17 0
 255&nbsp;echo -e '\E[?25l'Press [enter] key to start the race...
 256&nbsp;read -s
 257&nbsp;
 258&nbsp;#  Disable normal echoing in the terminal.
 259&nbsp;#  This avoids key presses that might "contaminate" the screen
 260&nbsp;#+ during the race.  
 261&nbsp;stty -echo
 262&nbsp;
 263&nbsp;# --------------------------------------------------------
 264&nbsp;# Start the race.
 265&nbsp;
 266&nbsp;draw_horses
 267&nbsp;echo -ne '\E[37;47m'
 268&nbsp;move_and_echo 18 1 $BLANK80
 269&nbsp;echo -ne '\E[30m'
 270&nbsp;move_and_echo 18 1 Starting...
 271&nbsp;sleep 1
 272&nbsp;
 273&nbsp;# Set the column of the finish line.
 274&nbsp;WINNING_POS=74
 275&nbsp;
 276&nbsp;# Define the time the race started.
 277&nbsp;START_TIME=`date +%s`
 278&nbsp;
 279&nbsp;# COL variable needed by following "while" construct.
 280&nbsp;COL=0    
 281&nbsp;
 282&nbsp;while [ $COL -lt $WINNING_POS ]; do
 283&nbsp;                   
 284&nbsp;          MOVE_HORSE=0     
 285&nbsp;          
 286&nbsp;          # Check if the random_1_9 function has returned a good value.
 287&nbsp;          while ! echo $MOVE_HORSE | grep [1-9] &#38;&#62; /dev/null; do
 288&nbsp;                MOVE_HORSE=`random_1_9`
 289&nbsp;          done
 290&nbsp;          
 291&nbsp;          # Define old type and position of the "randomized horse".
 292&nbsp;          HORSE_TYPE=`cat  horse_${MOVE_HORSE}_position | tail -n 1`
 293&nbsp;          COL=$(expr `cat  horse_${MOVE_HORSE}_position | head -n 1`)
 294&nbsp;          
 295&nbsp;          ADD_POS=1
 296&nbsp;          # Check if the current position is an handicap position. 
 297&nbsp;          if seq 10 7 68 | grep -w $COL &#38;&#62; /dev/null; then
 298&nbsp;                if grep -w $MOVE_HORSE $COL &#38;&#62; /dev/null; then
 299&nbsp;                      ADD_POS=0
 300&nbsp;                      grep -v -w  $MOVE_HORSE $COL &#62; ${COL}_new
 301&nbsp;                      rm -f $COL
 302&nbsp;                      mv -f ${COL}_new $COL
 303&nbsp;                      else ADD_POS=1
 304&nbsp;                fi 
 305&nbsp;          else ADD_POS=1
 306&nbsp;          fi
 307&nbsp;          COL=`expr $COL + $ADD_POS`
 308&nbsp;          echo $COL &#62;  horse_${MOVE_HORSE}_position  # Store new position.
 309&nbsp;                            
 310&nbsp;         # Choose the type of horse to draw.         
 311&nbsp;          case $HORSE_TYPE in 
 312&nbsp;                1) HORSE_TYPE=2; DRAW_HORSE=draw_horse_two
 313&nbsp;                ;;
 314&nbsp;                2) HORSE_TYPE=1; DRAW_HORSE=draw_horse_one 
 315&nbsp;          esac       
 316&nbsp;          echo $HORSE_TYPE &#62;&#62;  horse_${MOVE_HORSE}_position
 317&nbsp;          # Store current type.
 318&nbsp;         
 319&nbsp;          # Set foreground color to black and background to green.
 320&nbsp;          echo -ne '\E[30;42m'
 321&nbsp;          
 322&nbsp;          # Move the cursor to new horse position.
 323&nbsp;          tput cup `expr $MOVE_HORSE + 5` \
 324&nbsp;	  `cat  horse_${MOVE_HORSE}_position | head -n 1` 
 325&nbsp;          
 326&nbsp;          # Draw the horse.
 327&nbsp;          $DRAW_HORSE
 328&nbsp;           usleep $USLEEP_ARG
 329&nbsp;          
 330&nbsp;           # When all horses have gone beyond field line 15, reprint odds.
 331&nbsp;           touch fieldline15
 332&nbsp;           if [ $COL = 15 ]; then
 333&nbsp;             echo $MOVE_HORSE &#62;&#62; fieldline15  
 334&nbsp;           fi
 335&nbsp;           if [ `wc -l fieldline15 | cut -f1 -d " "` = 9 ]; then
 336&nbsp;               print_odds
 337&nbsp;               : &#62; fieldline15
 338&nbsp;           fi           
 339&nbsp;          
 340&nbsp;          # Define the leading horse.
 341&nbsp;          HIGHEST_POS=`cat *position | sort -n | tail -1`          
 342&nbsp;          
 343&nbsp;          # Set background color to white.
 344&nbsp;          echo -ne '\E[47m'
 345&nbsp;          tput cup 17 0
 346&nbsp;          echo -n Current leader: `grep -w $HIGHEST_POS *position | cut -c7`\
 347&nbsp;	  "                              "
 348&nbsp;
 349&nbsp;done  
 350&nbsp;
 351&nbsp;# Define the time the race finished.
 352&nbsp;FINISH_TIME=`date +%s`
 353&nbsp;
 354&nbsp;# Set background color to green and enable blinking text.
 355&nbsp;echo -ne '\E[30;42m'
 356&nbsp;echo -en '\E[5m'
 357&nbsp;
 358&nbsp;# Make the winning horse blink.
 359&nbsp;tput cup `expr $MOVE_HORSE + 5` \
 360&nbsp;`cat  horse_${MOVE_HORSE}_position | head -n 1`
 361&nbsp;$DRAW_HORSE
 362&nbsp;
 363&nbsp;# Disable blinking text.
 364&nbsp;echo -en '\E[25m'
 365&nbsp;
 366&nbsp;# Set foreground and background color to white.
 367&nbsp;echo -ne '\E[37;47m'
 368&nbsp;move_and_echo 18 1 $BLANK80
 369&nbsp;
 370&nbsp;# Set foreground color to black.
 371&nbsp;echo -ne '\E[30m'
 372&nbsp;
 373&nbsp;# Make winner blink.
 374&nbsp;tput cup 17 0
 375&nbsp;echo -e "\E[5mWINNER: $MOVE_HORSE\E[25m""  Odds: `cat odds_${MOVE_HORSE}`"\
 376&nbsp;"  Race time: `expr $FINISH_TIME - $START_TIME` secs"
 377&nbsp;
 378&nbsp;# Restore cursor and old colors.
 379&nbsp;echo -en "\E[?25h"
 380&nbsp;echo -en "\E[0m"
 381&nbsp;
 382&nbsp;# Restore echoing.
 383&nbsp;stty echo
 384&nbsp;
 385&nbsp;# Remove race temp directory.
 386&nbsp;rm -rf $HORSE_RACE_TMP_DIR
 387&nbsp;
 388&nbsp;tput cup 19 0
 389&nbsp;
 390&nbsp;exit 0</PRE
></TD
></TR
></TABLE
><HR></DIV
><P
>See also <A
HREF="contributed-scripts.html#HASHEXAMPLE"
>Example A-21</A
>, <A
HREF="contributed-scripts.html#HOMEWORK"
>Example A-44</A
>, <A
HREF="contributed-scripts.html#SHOWALLC"
>Example A-52</A
>, and <A
HREF="contributed-scripts.html#PETALS"
>Example A-40</A
>.</P
><DIV
CLASS="CAUTION"
><TABLE
CLASS="CAUTION"
WIDTH="100%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="common/caution.png"
HSPACE="5"
ALT="Caution"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>There is, however, a major problem with all
	  this. <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>ANSI escape sequences are emphatically
          <A
HREF="portabilityissues.html"
>non-portable</A
>.</I
></SPAN
>
          What works fine on some terminal emulators (or the
          console) may work differently, or not at all, on others.
          A <SPAN
CLASS="QUOTE"
>"colorized"</SPAN
> script that looks stunning on the
          script author's machine may produce unreadable output on
          someone else's. This somewhat compromises the usefulness of
          colorizing scripts, and possibly relegates this technique
          to the status of a gimmick. Colorized scripts are probably
          inappropriate in a commercial setting, i.e., your supervisor
          might disapprove.</P
></TD
></TR
></TABLE
></DIV
><P
>Alister's <A
HREF="http://code.google.com/p/ansi-color/"
TARGET="_top"
>          ansi-color</A
> utility (based on <A
HREF="http://bash.deta.in/color-1.1.tar.gz"
TARGET="_top"
>Moshe
          Jacobson's color utility</A
> considerably simplifies using
          ANSI escape sequences. It substitutes a clean and logical
          syntax for the clumsy constructs just discussed.</P
><P
>Henry/teikedvl has likewise created a utility (<A
HREF="http://scriptechocolor.sourceforge.net/"
TARGET="_top"
>http://scriptechocolor.sourceforge.net/</A
>) to simplify creation of colorized scripts.</P
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
BORDER="0"
CLASS="FOOTNOTES"
WIDTH="100%"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN20259"
HREF="colorizing.html#AEN20259"
>[1]</A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
><SPAN
CLASS="ACRONYM"
>ANSI</SPAN
> is, of course, the
	     acronym for the American National Standards
	     Institute. This august body establishes and maintains
	     various technical and industrial standards.</P
></TD
></TR
></TABLE
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