236 lines
3.6 KiB
HTML
236 lines
3.6 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>PROMPT_COMMAND</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="External Commands"
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HREF="c262.html"><LINK
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REL="PREVIOUS"
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TITLE="External Commands"
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HREF="c262.html"><LINK
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REL="NEXT"
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TITLE="External Commands in the Prompt"
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HREF="x279.html"></HEAD
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><BODY
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CLASS="SECT1"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><DIV
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CLASS="NAVHEADER"
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SUMMARY="Header navigation table"
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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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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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><A
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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 4. External Commands</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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><A
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>Next</A
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></TD
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></TR
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><HR
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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="AEN264"
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></A
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>4.1. PROMPT_COMMAND</H1
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><P
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>Bash provides an environment variable called <TT
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CLASS="ENVAR"
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>PROMPT_COMMAND</TT
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>.
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The contents of this variable are executed as a regular Bash command just
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before Bash displays a prompt. </P
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><TABLE
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BORDER="1"
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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="SCREEN"
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>[21:55:01][giles@nikola:~] PS1="[\u@\h:\w]\$ "
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[giles@nikola:~] PROMPT_COMMAND="date +%H%M"
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2155
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[giles@nikola:~] d
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bin mail
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2156
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[giles@nikola:~] </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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>What happened above was that I changed PS1 to no longer include the
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<TT
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CLASS="USERINPUT"
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><B
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>\t</B
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></TT
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> escape sequence (added in a previous section), so
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the time was no longer a part of the prompt. Then I used <TT
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CLASS="USERINPUT"
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><B
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>date
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+%H%M</B
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></TT
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> to display the time in a format I like better. But it
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appears on a different line than the prompt. Tidying this up using
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<TT
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CLASS="USERINPUT"
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><B
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>echo -n ...</B
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></TT
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> as shown below works with Bash 2.0+, but
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appears not to work with Bash 1.14.7: apparently the prompt is drawn in a
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different way, and the following method results in overlapping text. </P
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><TABLE
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BORDER="1"
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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="SCREEN"
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>2156
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[giles@nikola:~] PROMPT_COMMAND="echo -n [$(date +%H%M)]"
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[2156][giles@nikola:~]$
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[2156][giles@nikola:~]$ d
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bin mail
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[2157][giles@nikola:~]$ unset PROMPT_COMMAND
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[giles@nikola:~]</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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><TT
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CLASS="USERINPUT"
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><B
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>echo -n ...</B
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></TT
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> controls the output of the
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<B
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CLASS="COMMAND"
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>date</B
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> command and suppresses the trailing newline,
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allowing the prompt to appear all on one line. At the end, I used the
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<B
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CLASS="COMMAND"
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>unset</B
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> command to remove the
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<TT
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CLASS="ENVAR"
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>PROMPT_COMMAND</TT
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> environment variable. </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="c262.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="x279.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%"
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ALIGN="left"
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VALIGN="top"
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>External Commands</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="c262.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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>External Commands in the Prompt</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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> |