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<TITLE>The Answer Guy 51: ksh Keybindings (vi Keys)</TITLE>
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<H4>"The Linux Gazette...<I>making Linux just a little more fun!</I>"</H4>
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<H1><A NAME="answer">
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<H4>By James T. Dennis,
<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a><BR>
LinuxCare,
<A HREF="http://www.linuxcare.com/">http://www.linuxcare.com/</A>
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<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>ksh Keybindings (vi Keys)</H3>
<p><strong>From Robert Lynch on Sun, 20 Feb 2000
</strong></p>
<!-- ::
ksh Keybindings (vi Keys)
~~~~~~~~~~~~~~~~~~~~~~~~~
:: -->
<P><STRONG>
Hi-
</STRONG></P>
<P><STRONG>
My wife is an SCO sys admin whose business bought her a Dell
pre-configured RH 6.0 box for home use. She's used to ksh on SCO, with
default vi setting. She finds this broken with bash. I have tried
to fix it, including installing pdksh, but no joy.
</STRONG></P>
<P><STRONG>
Say she types:
</STRONG></P>
<Pre><STRONG>$ ls
$ who
</STRONG></Pre>
<P><STRONG>
then hits ESC + up arrow. Instead of moving through the command
history, a "[A" character appears. I tried re-mapping the arrow keys
but nada.
</STRONG></P>
<P><STRONG>
Please NOTE: I've been working on this for a while, and have seen
several postings, to the effect "just set -o vi". Ain't this!
</STRONG></P>
<P><STRONG>
TIA. Bob L.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
<tt>set -o vi</tt> under bash works fine for me. I've used it
occasionally and I've had students use it for years.
</BLOCKQUOTE>
<BLOCKQUOTE>
However, vi normally uses the letters h,j,k, and l for its
cursor controls. The [Up Arrow] and other keys are not
traditional vi key bindings (though most modern versions of
vi will also accept them if your terminal is properly
configured using the appropriate <tt>TERM</tt> variable in
association with a decent terminfo or termcap entry).
</BLOCKQUOTE>
<BLOCKQUOTE>
Can you run '<tt>vi</tt>' (the editor) and/or emacs or xemacs from
this command prompt? Is it in an xterm or from a text
console? Are you (and she) accessing this through telnet?
What terminal emulation is this going through?
</BLOCKQUOTE>
<BLOCKQUOTE>
If you can run '<tt>vi</tt>' or '<tt>emacs</tt>' within that terminal window,
or console/terminal session then your <tt>TERM</tt> environment
setting should be sufficient to support the vi keybindings
used by bash, pdksh and ksh). My quick tests with pdksh, ksh
'93, and bash all show that the [Up Arrow] key IS recognized
by the vi keys handlers in any of them. I tested this from
a text console with <tt>TERM=linux</tt>, from under the '<tt>screen</tt>'
utility with <tt>TERM=screen</tt>, and from an xterm with <tt>TERM=xterm</tt>.
This is all on a <A HREF="http://www.debian.org/">Debian</A>/Potato system
with all recent updates applied for all software (yesterday).
</BLOCKQUOTE>
<BLOCKQUOTE>
So I don't know what is wrong. You'll want to play with the
'k' (vi up key) to see if that works, and play with the TERM
variable (especially if you're connecting through your net
using some MS-DOS or MS-Windows telnet client). You might
also want to check if you are using some unusual key
mappings on your Linux console (the loadkeys command) or in
your copy of X (the xmodmap command). Again, if you have
vi and emacs working normally, then these should not be
problems for you.
</BLOCKQUOTE>
<BLOCKQUOTE>
Moving on to the larger issues of making your wife feel at
home on here new system. If she's used to SCO's ksh then
she might find some of the minor differences between it and
GNU bash (the default Linux shell, from the Free Software
Foundation --- <A HREF="http://www.gnu.org"
>http://www.gnu.org</A>). There are even
differences between pdksh and ksh '93, and even more minor
ones between pdksh and ksh '88.
</BLOCKQUOTE>
<BLOCKQUOTE>
I don't know which ksh ships with SCO UNIX nor even which
version of SCOnix that your wife is using. I'll assume
she's using a recent copy, and that it shipped with the most
recent Korn shell.
</BLOCKQUOTE>
<BLOCKQUOTE>
I suppose the best advice would be to get the real Korn
Shell (ksh '93) from David G. Korn's web site:
<A HREF="http://www.kornshell.com"
>http://www.kornshell.com</A>. Just follow a couple of obvious
links (Software, "Official AT&amp;T Release...") and fill out
the little form.
</BLOCKQUOTE>
<BLOCKQUOTE>
Note that this is NOT free for commercial use. It is also
NOT open source. You can read their license agreement for
all of the details.
</BLOCKQUOTE>
<BLOCKQUOTE>
If your use will be within those restrictions than you can
get this for your wife. If she's used to subtle nuances of
ksh --- and especially if she does serious shell scripting
involving associative arrays, co-processes, and floating
point mathematics then she'll be happier with the "real
thing" then she will be with bash or pdksh.
</BLOCKQUOTE>
<BLOCKQUOTE>
Most shell users wouldn't know the difference. However, ksh
'93 (the most recent major release of the package) is the
"king" of Unix command shells. It has a number of features
which are unique to it (particularly in support of
associative arrays).
</BLOCKQUOTE>
<BLOCKQUOTE>
There's a pretty good, and short, article co-authored by the
creator of the Korn shell that discusses some of the
features that make ksh '93 unique which was published by the
Linux Journal and can be read on their web site at:
</BLOCKQUOTE>
<BLOCKQUOTE><BlockQuote>
<A HREF="http://www2.linuxjournal.com/cgi-bin/frames.pl/lj-issues/issue27/korn.html"
>http://www2.linuxjournal.com/cgi-bin/frames.pl/lj-issues/issue27/korn.html</A>
</BlockQuote></BLOCKQUOTE>
<BLOCKQUOTE>
More information about pdksh can be found at the web site of
its current maintainer, Michael Rendell at:
</BLOCKQUOTE>
<BLOCKQUOTE><BlockQuote>
<A HREF="http://www.cs.mun.ca/~michael/pdksh"
>http://www.cs.mun.ca/~michael/pdksh</A>
</BlockQuote></BLOCKQUOTE>
<BLOCKQUOTE>
As far as I know pdksh and ksh are the only shells to
support co-processes. So, if your wife uses those she'll
definitely want to use one of them. Bash doesn't seem to
support co-processes, yet. I think it's on their wishlist.
</BLOCKQUOTE>
<BLOCKQUOTE>
(For those that don't know: Co-processes work something
like this:
</BLOCKQUOTE>
<blockquote><pre> $ bc |&amp;
[1] 12345
$ print -p '1234 * 4567890'
$ read -p result
$ echo $result
...
$ print -p quit
$
[1] + Done bc
$
</pre></blockquote>
<BLOCKQUOTE>
I started a copy of the "big calculator" (bc). The |&amp;
operator makes it a "co-process" --- running with its
stdin (standard input file stream) connected to one
pipe from ksh/pdksh and its stdout (standard output
file stream) connected to another. Then I printed
a value into that special co-process pipe (print -p)
and read that value back out (using read -p). I can
then print other transactions into this co-process and
read other results from it. This allows me to have
one process loaded, maintaining state, and available
for work. In shells that don't support co-processes
I'd have to maintain my own state, and keep re-executing
this command (possibly with quite a bit of extra
over-head in providing my intermediate results/state
back to the new instance of the program).
</BLOCKQUOTE>
<BLOCKQUOTE>
So, co-processes are one of the more interesting innovations
of the Korn shell. Such things are relatively easy to do
from C, but ksh and pdksh are the only shells that
interactively provide these at a high level shell prompt.)
</BLOCKQUOTE>
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<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
>Copyright &copy;</a> 2000, James T. Dennis
<BR>Published in <I>The Linux Gazette</I> Issue 51 March 2000</H5>
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