[squeak-dev] [OSProcess] How to read the stdout of a process running an infinite loop?

Hi,

Gautier and I have a software written in C that loops infinitly doing  
some computations. At every iteration it displays something on the  
shell. We want to read the output into squeak. We can not wait for the  
end of the computations, since it's an infinite loop :-)

Any hints?

Thanks,
Noury
------------------------------------------------------------------
Dr. Noury Bouraqadi - Enseignant/Chercheur
Responsable de l'enseignement de l'informatique
ARMINES - Ecole des Mines de Douai - Dept. I.A.
http://vst.ensm-douai.fr/noury

European Smalltalk Users Group Board
http://www.esug.org
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On Tue, May 20, 2008 at 05:10:45PM +0200, Noury Bouraqadi wrote:
> Hi,
>
> Gautier and I have a software written in C that loops infinitly doing  
> some computations. At every iteration it displays something on the  
> shell. We want to read the output into squeak. We can not wait for the  
> end of the computations, since it's an infinite loop :-)
>
> Any hints?

I don't have Squeak system to look at right now, but the way to do
this is to use a PipeableOSProcess and register an interest in data
available. Load CommandShell in addition to OSProcess to get the
necessary classes.

One of the SUnit test suites in the CommandShell shows how the
#changed:/#update: notifications are set up for a CommandShell window.
For your application, I think you can just add a dependent to your
instance of PipeableOSProcess to get the data available notification
(but I don't remember the details of how I set this up).

Class ProxyPipeline is a good way to start your C program, see the
class side examples. This can be used to create a PipeableOSProcess
that runs your C program, and you can get #changed: notifications
whenever data becomes available on the pipe from the C program. Use
PipeableOSProcess>>upToEnd to read the data (note, there is also an
#upToEndOfFile method that reads all data until your C program
terminates - that is not what you want).

It is best if your VM has AioPlugin in addition to OSProcessPlugin,
but it will work even without this (a polling loop will be used
instead of real aio events).

Dave

On Tue, May 20, 2008 at 05:10:45PM +0200, Noury Bouraqadi wrote:
> Hi,
>
> Gautier and I have a software written in C that loops infinitly doing  
> some computations. At every iteration it displays something on the  
> shell. We want to read the output into squeak. We can not wait for the  
> end of the computations, since it's an infinite loop :-)
>
> Any hints?

Try the attached change set for an example. I made a shell script that
generates output, named it "test.sh", and ran it from Squeak as follows.

        | proxyWatcher |
        proxyWatcher := ReadFromExternalProgram programName: 'test.sh'.
        proxyWatcher start.
        (Delay forSeconds: 10) wait.
        proxyWatcher stop.

The proxyWatcher runs the external program for 10 seconds, copying its
output to the Transcript as new data becomes available.

Hope this helps,
Dave

Thanks David. We'll give it a try.

Noury
On 21 mai 08, at 04:48, David T. Lewis wrote:

Noury Bouraqadi
------------------------------------------------------------------
Dr. Noury Bouraqadi - Enseignant/Chercheur
Responsable de l'enseignement de l'informatique
ARMINES - Ecole des Mines de Douai - Dept. I.A.
http://vst.ensm-douai.fr/noury

European Smalltalk Users Group Board
http://www.esug.org
------------------------------------------------------------------