Nick Craig-Wood wrote:
> Adrian Casey <[EMAIL PROTECTED]> wrote:
>> > Adrian Casey <[EMAIL PROTECTED]> wrote:
>> > import os, pexpect, threading
>> >
>> > def runyes():
>> > print "Running yes command..."
>> > pexpect.run('yes', timeout=5)
>> >
>> > t = threading.Thread(target=runyes)
>> > t.start()
>> > t.join()
>> >
>> The timeout parameter will not work in this case. If you run the sample
>> code above, it will run forever.
>
> The above runs just fine for me, stopping after 5 seconds. Did you
> try it?
>
>> The 'yes' command presents a class of command which can not be
>> easily be handled by pexpect.
>
> Worked for me under Debian/testing.
>
>> As far as I know, mixing threads and signals is OK provided the
>> parent creates the alarm.
>
> There are so many pitfalls here that I advise you not to try. From
> the linuxthreads FAQ
>
> J.3: How shall I go about mixing signals and threads in my program?
>
> The less you mix them, the better. Notice that all pthread_*
> functions are not async-signal safe, meaning that you should not
> call them from signal handlers. This recommendation is not to be
> taken lightly: your program can deadlock if you call a pthread_*
> function from a signal handler!
>
> The only sensible things you can do from a signal handler is set a
> global flag, or call sem_post on a semaphore, to record the delivery
> of the signal. The remainder of the program can then either poll the
> global flag, or use sem_wait() and sem_trywait() on the semaphore.
>
> Another option is to do nothing in the signal handler, and dedicate
> one thread (preferably the initial thread) to wait synchronously for
> signals, using sigwait(), and send messages to the other threads
> accordingly.
>
> Note also that the signal can be delivered to any thread which
> complicates things.
>
I'm running Kubuntu 06-06 with python 2.4.3 and the above code runs forever
at 100% cpu utilization. I shall look into semaphores. However, that means
another thread whose sole purpose is to watch the semaphore.
Thanks for you help.
Cheers.
Adrian.
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