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From: hsu@cobra.gatech.edu (Yung-Kao Hsu)
Newsgroups: comp.lang.smalltalk
Subject: Re: Anyway to run a program directly from smalltalk?
Message-ID: <19570@mephisto.UUCP>
Date: 22 Feb 90 01:31:51 GMT
References: <19566@mephisto.UUCP> <77422@tut.cis.ohio-state.edu>
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Reply-To: hsu@cobra.UUCP (Yung-Kao Hsu)
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Organization: ICS, Georgia Tech.
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In article <77422@tut.cis.ohio-state.edu> Timothy Hansell writes:
>
>In article <19566@mephisto.UUCP> hsu@boa.gatech.edu (Yung-Kao Hsu) writes:
>>...
>>The problem could be greatly reduced if somehow I could build
>>an object that could run a "prolog" or any other process directly
>>by sending a message to it. Has anyone here known of such thing?
>
>If you look at the Terminal object you will see that it is invoking the
>c-shell and then passing through commands from the user to the shell. It
>is possible to use this same connection that is used by the Terminal to
>send command strings directly to the shell. I've seen it done on some
> ...
>---
>Tim Hansell
>hansell@cis.ohio-state.edu
>P.O. Box 687 South Charleston, Ohio, 45268


I did acknowledge such possibility. However I have been hesitated to
take this approach since I don't have enough document and my exprience
a while ago only bring some troubles. But after seeing Tim's reply, I
realized this might be the only way to solve the problem. Sure enough,
couples of hours in examining the behaviors of Terminal using single
steps, I did figure out how to write a method on CShellPort that acts
like unix's `system' call.

The main question was to ensure the synchronization between the caller
and callee since you could send a shell command for execution but it
could return before the command is done. I adopt an ad hoc strategy to
solve this problem by waiting on the return of csh's prompt (thus the
pattern of the prompt needs to be part of the method). However, this
could be avoided if there's no terminal output for command's execution
where a single wait on any response will be enough.

At this moment, the problem seems to be solved and I would like to
Tim very much for his insighted suggestions that leading me to solve
this problem. For anyone who might be interested at my solution, a
brief outline is given below.

--------------
1) For creating a CShell interface:

	Unix _ CShellPort open.
	Unix receiveBuffer.	"for the initial prompt".

2) For `system':

system: commandStringWithCR
| completed |

	completed _ false.
	Unix sendBuffer: commandStringWithCR.  "make sure a CR exists"
	[ completed ]
	whileFalse: [
		Unix receiveBuffer.
		echo _ Unix receivedString.
		( promptPattern match: echo)
		ifTrue: [
			completed _ true ].
		"do anything you want with the response here" ].

where
	* promptPattern: string constant for csh's prompt pattern.
	* the method receivedString obtain the response from csh.
	  This method can be written following the method
	  `displayCharacters' in class Terminal.
	* Don't forget to release the port after the port is no
	  longer needed.

PS: I couldn't quite believe the solution is so simple but suppose
that is exactly what you could get from a programming environment.
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