239 lines
4.1 KiB
HTML
239 lines
4.1 KiB
HTML
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<HTML
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><HEAD
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><TITLE
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>Controlling the Size and Appearance of $PWD</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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REL="HOME"
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TITLE="Bash Prompt HOWTO"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="Prompt Code Snippets"
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HREF="c679.html"><LINK
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REL="PREVIOUS"
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TITLE="Number of Processes"
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HREF="x771.html"><LINK
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REL="NEXT"
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TITLE="Laptop Power"
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HREF="x794.html"></HEAD
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CLASS="SECT1"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Bash Prompt HOWTO: </TH
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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HREF="x771.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 11. Prompt Code Snippets</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="AEN783"
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></A
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>11.10. Controlling the Size and Appearance of $PWD</H1
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><P
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>Unix allows long file names, which can lead to the value of $PWD being very
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long. Some people (notably the default RedHat prompt) choose to use the
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basename of the current working directory (ie. "giles" if
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$PWD="/home/giles"). I like more info than that, but it's often desirable
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to limit the length of the directory name, and it makes the most sense to
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truncate on the left.</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="PROGRAMLISTING"
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># How many characters of the $PWD should be kept
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local pwdmaxlen=30
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# Indicator that there has been directory truncation:
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#trunc_symbol="<"
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local trunc_symbol="..."
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if [ ${#PWD} -gt $pwdmaxlen ]
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then
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local pwdoffset=$(( ${#PWD} - $pwdmaxlen ))
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newPWD="${trunc_symbol}${PWD:$pwdoffset:$pwdmaxlen}"
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else
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newPWD=${PWD}
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fi </PRE
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></FONT
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></TD
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></TR
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></TABLE
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><P
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>The above code can be executed as part of PROMPT_COMMAND, and the
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environment variable generated (<TT
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CLASS="VARNAME"
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>newPWD</TT
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>) can then
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be included in the prompt. Thanks to Alexander Mikhailian
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<TT
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CLASS="EMAIL"
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><<A
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HREF="mailto:mikhailian at altern dot org"
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>mikhailian at altern dot org</A
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>></TT
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> who rewrote the code to utilize
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new Bash functionality, thus speeding it up considerably. </P
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><P
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>Risto Juola (risto AT risto.net) wrote to say that he preferred to have the
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"~" in the <TT
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CLASS="VARNAME"
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>$newPWD</TT
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>, so he wrote another version: </P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="PROGRAMLISTING"
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>pwd_length=20
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DIR=`pwd`
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echo $DIR | grep "^$HOME" >> /dev/null
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if [ $? -eq 0 ]
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then
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CURRDIR=`echo $DIR | awk -F$HOME '{print $2}'`
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newPWD="~$CURRDIR"
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if [ $(echo -n $newPWD | wc -c | tr -d " ") -gt $pwd_length ]
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then
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newPWD="~/..$(echo -n $PWD | sed -e "s/.*\(.\{$pwd_length\}\)/\1/")"
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fi
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elif [ "$DIR" = "$HOME" ]
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then
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newPWD="~"
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elif [ $(echo -n $PWD | wc -c | tr -d " ") -gt $pwd_length ]
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then
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newPWD="..$(echo -n $PWD | sed -e "s/.*\(.\{$pwd_length\}\)/\1/")"
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else
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newPWD="$(echo -n $PWD)"
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fi</PRE
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></FONT
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></TD
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></TR
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></TABLE
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><P
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>Relative speed: the first version takes about 0.45 seconds on an
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unloaded 486SX25. Risto's version takes about 0.80 to 0.95 seconds. The
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variation in this case is due to whether or not truncation is required. </P
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></DIV
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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SUMMARY="Footer navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="x771.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="index.html"
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ACCESSKEY="H"
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>Home</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="x794.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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><TR
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><TD
|
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|
WIDTH="33%"
|
||
|
ALIGN="left"
|
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|
VALIGN="top"
|
||
|
>Number of Processes</TD
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||
|
><TD
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||
|
WIDTH="34%"
|
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|
ALIGN="center"
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VALIGN="top"
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><A
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HREF="c679.html"
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ACCESSKEY="U"
|
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|
>Up</A
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></TD
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><TD
|
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|
WIDTH="33%"
|
||
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ALIGN="right"
|
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VALIGN="top"
|
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>Laptop Power</TD
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></TR
|
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|
></TABLE
|
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></DIV
|
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></BODY
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></HTML
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>
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