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kstart child PID

fabienhenon

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Tuesday, June 7th 2005, 10:09pm

kstart child PID

Hi .

I am writing an editor for Linux for the POV-RAY raytracer (with wxpython GUI).

When the user clicks on render I use 'kstart --ontop povray ...' to launch the render on top. The problem is that I need to know the PID of povray to read the output.

I get the PID of kstart ( that dies when povray is started ), but I do not get the child PID.

Does anyone have an idea ?


Thanks
fabien
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anda_skoa

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Wednesday, June 8th 2005, 3:19pm

Maybe running a script and having it write the PID to some temporary file or a pipe.

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fabienhenon

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Wednesday, June 8th 2005, 10:54pm

Yes but how do you get the PID number of the app launched by kstart ?
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anda_skoa

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Thursday, June 9th 2005, 10:47am

When writing the PID of the real program into a file inside the script, the PID of the script doesn't matter, does it?

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fabienhenon

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Thursday, June 9th 2005, 12:26pm

with the python script below :

f=popen2.Popen4('kstart --ontop povray +itest.pov',1)
az=f.pid

az returns the PID number of kstart, not the PID NUMBER of povray


whereas with
f=popen2.Popen4('povray +itest.pov',1)
az=f.pid

az returns the PID number of povray.

I need to know the PID number to check whether the render is still running and to read the output stream.

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fabien
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anda_skoa

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Thursday, June 9th 2005, 3:16pm

So are you ignoring my initial suggestion or did I just not get through that you ought to start a script instead of povray and have the script write the PID into a file or PIPE?

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fabienhenon

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Thursday, June 9th 2005, 7:00pm

Sorry, but I do not understand ( back from work, dumbness overwhelms me)...

What do you suggest ?
Sure, I can use a script that writes the child PID into a pipe, but I just do not know how to retrieve it.

with this command...
f=popen2.Popen4('kstart --ontop povray +itest.pov',1)

kstart spawns a child, but I cannot get the PID of its child.


If you have even a tiny script, please enclose it.

Thanks for enduring this.

Fabien
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jacek

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Thursday, June 9th 2005, 7:29pm

Quoted

Originally posted by fabienhenon
with this command...
f=popen2.Popen4('kstart --ontop povray +itest.pov',1)

f.pid ?

anda_skoa

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Thursday, June 9th 2005, 9:07pm

Quoted

Originally posted by fabienhenon
What do you suggest ?
Sure, I can use a script that writes the child PID into a pipe, but I just do not know how to retrieve it.


By reading the file/pipe?

For example in bash you can do this

Source code

 
1
2

povray $@ &
echo $! > $(kdeconfig --path tmp)/povray.pid


Then read povray.pid from the KDE tmp location
I guess an advanced script language like Python can do this as well.

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fabienhenon

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Friday, June 10th 2005, 5:27pm

Hi,

With the script below :
povray $@ &
echo $! > $(kdeconfig --path tmp)/povray.pid

I can get povray pid



With the script below :
kstart povray $@ &
echo $! > $(kdeconfig --path tmp)/povray.pid

I can get kstart pid, not povray pid (and that is what I want)


Cheers,
Fabien
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anda_skoa

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Saturday, June 11th 2005, 1:10pm

Quoted

Originally posted by fabienhenon
With the script below :
kstart povray $@ &
echo $! > $(kdeconfig --path tmp)/povray.pid

I can get kstart pid, not povray pid (and that is what I want)


Obviously, as you again use povray as the command for kstart instead of the script.

Do you think creating a script and putting it somewhere help when you don't change the command you are calling?

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