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Date:	Mon, 6 Mar 2000 05:47:37 PST
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: Re: korn shell

Content Type: text/plain

dallasii@kincyb.com wrote:
>
> The thing in my mind that defines UNIX at the command line
> prompt is that each stage in a pipe occurs as a process
> that happens in parallel to the other stages of the pipe.
>
> As far as I know, this is not the case for all versions of
> DOS, OS/2, and any products from M$.

OS/2 parallels its command line "pipes" - I believe it's documented
(don't remember where) and the command line filters I run seem to act
accordingly.

I just tested the following on a large partition and the output appears
instantly, hence there's no "temporary" file on disk:

cd \
dir /s | find " "

The above starts in the root directory and does a DIR list of every file
on the drive. The FIND simply copies every line, since every line
contains at least one space.

DOS and DOS-based versions of Windows use a temporary file for a pipe.
_____

> Also the process control seems to be an area that OS/2
> doesn't quite have all the fine points that UNIX has.
> The little 'go' utility seems to provide rough
> equivalants to 'kill', 'ps' and 'fg' (restart in
> foreground), but what to replace the suspend character
> '^Z' and 'bg' (restart in background) with I don't
> know - maybe someone else has some suggestions?

Clueless here. I don't know anything about go, kill, ps, fg, bg and the
^Z suspend character. Are these all Unix commands?

> Another area I recall he had to make provision for is
> to handle file extensions, which was especially useful
> for .CMD files. The context that korn shell came up
> on this list was my finding that he didn't get it
> perfect, and some special provision was needed for
> putting REXX filters in pipes.

For those who've never seen a filter in Rexx, following is the framework
code from rxtt28 (a Rexx info file currently at version 30 [rxtt30] -
it's on Hobbes). I may have modified it slightly, I don't remember. (I
probably reformatted it since I indent all my "end" statements and
that's how this code is formatted.)

/* The FILTER.CMD Rexx program is a sample filter. It was taken from
RXTT28. */

/* Programmer's notes:
/ 1. Write all messages (error messages, logos, etc.) to STDERR
instead of STDOUT, e.g. use
/ call lineout 'STDERR', 'This is an error message'
/ 2. Always use
/ call trace 'OFF'
/ as the first statement in a filter program. This statement
makes sure that your program
/ ignores the environment variable RXTRACE.
/ 3. The function LINES() does not work as expected in
Object-Oriented REXX (it always returns
/ 0). Therefore, you must distinguish between the different
REXX versions in your filter
/ program.
/ 4. A filter program reads lines from STDIN and writes lines to
STDOUT.
/ */

/* Ignore the environment variable RXTRACE. */
call trace 'OFF'

/* 'SIGNAL ON NOTREADY NAME' catches the end-of-file condition. */
signal on notready name ProgramEnd

/* Check the REXX interpreter version. 'PARSE VERSION' is a REXX
command. */
parse version rexxVersion .
if rexxVersion = 'OBJREXX'
then do
/* Current REXX version is Object REXX. */
/* Main loop for Object REXX. */
/* (The loop is exited by a NOTREADY condition.) */
do forever
.output~lineout( .input~linein )
end
end
else do
/* Current REXX version is Classic REXX. */
/* Main loop for Classic REXX. */
do while lines( 'STDIN' ) <> 0
call lineout 'STDOUT', linein()
end
end

ProgramEnd:
exit 0
_____

> PS> And just out of curiosity, can ksh (if that's the name) be run _from_
> PS> CMD.EXE or do you have to modify the CONFIG.SYS line (SET
> PS> OS2_SHELL=x:\OS2\CMD.EXE)?
>
> Either way works fine, as I recall.
> My experience was that it's easiest not to completely scrap CMD.EXE,
> but to change your thinking about it. It's not a shell but a
> library of functions that are still useful in their own right.
> Between those, and what sed provides, with a few
> wrapper shell functions and alias's, you can emulate
> most of the basic UNIX commands, without cluttering up your
> file system with an excess of EMX ports of rather minor
> programs.

Good info, thanks.
_____

- Peter

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