Re: The "Right Way" (TM) to run external program out of gtk2-perl app?

[Stephan Brunner <stephan brunner gmx de>]

Hi muppet and list,

Am Dienstag 30 August 2005 17:23 schrieb muppet:
> Stephan Brunner said:
> > What is the most safe and clean way of calling convert?
> > My requirements are
> > 1) portability (Linux + Win32)
> > 2) check exit status of convert
> > 3) no need to write to or read from convert (no pipe needed)
> > 4) UI blocking not nice, but would be acceptable
> > 5) only one instance of convert at a time
> > 6) the subroutine calling convert must not return until convert is done,
> > because I need to do some updates (ProgressBar, image display, ...)
> > afterwords, and to hold for 5.
> >
> > I tried the solution for long-file-reading in the FAQ with
> > Helper::add_watch, but it doesn't hold for 6). Didn't try it on win32.
>
> To make the long-file-read approach work for 6), you simply need to run a
> nested main loop, and kill that nested main loop when the operation is
> finished.  Then you can wrap that whole thing up in a function that blocks
> from the caller's point of view, but doesn't prevent the main loop from
> running.

[code]

> You said you didn't want pipes, but doing this form of IPC without a perl
> pipe open (which perl has conveniently made portable for us) is hard to get
> right, using fork(), wait(), SIGCHLD, and all sorts of delicate error
> handling.

I don't *need* pipes, but I don't mind using one if it works fine.

> This solution works nicely for me, and took about five minutes 
> to toss together in a working, if primitive, thumbnailer (see attached
> file).  Note that i have not tested this anywhere but on my linux desktop
> machine; YMMV.

This is quite frustrating, you solving my afternoons problem in five 
minutes:-) The solution you posted works perfect for me on Debian Sarge and 
Windows XP.
I found the reboot-issue not to be connected with this, because I can make my 
machine reboot also by calling "convert" in a (long enough) bash for-loop. 
Anyway, I do now have an always-responsive UI.

> Making it possible to kill the child in a 'cancel' action is left as an
> exercise for the reader.  ;-)

Hmm, for now, the well-honoured users (that is me, myself and I) will have to 
wait for the last called convert to finish its operation...

I very much appreciate your help, thank you!

Stephan