Re: how to kill a subprocess nicely?

[rsmith xs4all nl]

On  2 Aug, Thomas Niederreiter wrote:
> Hi there,
> 
> I have a question that may not be directly correlated to GTK, but
> perhaps some of you has an idea...
> 
> In my GTK-App I start a subprocess via fork and
> execl("/bin/sh", "sh", "-c", cmd ,NULL)
> 
> Then I set a gdk_input_add on this to get the output of the subprocess...
> all is working very nicely. Just one problem. 
> I have an "Abort" button in my GUI which should cause that the subprocess
> terminates. 
> 
> I tried to send an SIGINT via kill-command to the pid I get back from
> the fork (which is the /bin/sh...). But the Shell does not pass this
> signal to its child (my subprocess). 
> According to kill(2) manpage sending the signal to an negative pid should
> also kill all in the same process-group. I tried that too..but the child
> runs happily along. If I patch my subprocess to output at startup its
> own pid and I pick this output up and send my SIGINT to this pid everything
> works as expected. 

You could exec your app directly, using two pipe(2)s that you can link
to the child's standard input/output via fcntl(2) or dup2(2).

That way you can have two-way communication with the exec-ed process
and you can kill it easily. Or you could send a stop command to the
process via the pipe.

If you want an example, take a look at the plug-in code of the Giram 3D
modeller. I would think that the Gimp does something similar, but I
don't know where to find it in the source.

Roland
-- 
Roland Smith                      "Time is what prevents everything
r s m i t h @ x s 4 a l l . n l    from happening at once"

http://www.xs4all.nl/~rsmith/