To: python-list@python.org
From: Akira Li <4kir4.1i@gmail.com>
Subject: Re: How to make subprocess run for 60 sec?
Date: Fri, 12 Dec 2014 23:41:02 +0300
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Dan Stromberg <drsalists@gmail.com> writes:

> On Fri, Dec 12, 2014 at 12:48 AM, Robert Clove <cloverobert@gmail.com> wrote:
>> Hi All,
>>
>> I have the following python script that runs.
>> I want is to run the subprocess to run for 60 sec and then send the SIGINT
>> signal to subprocess and write the output in file.
>>
>> #!/usr/bin/python
>> import os
>> import subprocess
>> PIPE = subprocess.PIPE
>> import signal
>> import time
>>
>> def handler(signum, frame):
>>     pass
>>
>> signal.signal(signal.SIGALRM, handler)
>> signal.alarm(60)
>> command = "strace -c ./server"
>> os.chdir("/root/Desktop/")
>> p = subprocess.Popen(command, stdout=PIPE, stderr=PIPE)
>> time.sleep(60)
>> p.send_signal(signal.SIGINT)
>> signal.alarm(0)
>> print p.communicate()[1]
>
> Perhaps try something like:
>
> #!/usr/bin/python
>
> #import os
> import subprocess
> PIPE = subprocess.PIPE
> import signal
> import time
>
> #def handler(signum, frame):
> #    pass
>
> with open('output.txt', 'w') as out_file:
>     #signal.signal(signal.SIGALRM, handler)
>     #signal.alarm(60)
>     #command = "strace -c ./server"
>     command = "./test-script"
>     #os.chdir("/root/Desktop/")
>     p = subprocess.Popen(command, stdout=out_file, stderr=out_file, shell=True)
>     time.sleep(5)
>     p.send_signal(signal.SIGINT)
>     #signal.alarm(0)
>     #print p.communicate()[1]
>
> with open('output.txt', 'r') as in_file:
>     output = in_file.read()
>
> print(output)

You should probably call p.wait() after p.send_signal(), to wait until
the child process exits (possibly properly flushing its stdout buffer). 
It might make the output.txt content less garbled.

>
> BTW, killing an active strace may leave strace's subprocess stuck in
> an unkillable state.
>
> Also note that this will sleep for n seconds whether the subprocess
> takes that long or not.

The answer on StackOverflow [1] shows how to avoid waiting n seconds if the
subprocess finishes sooner.

[1] http://stackoverflow.com/questions/27443480/how-to-make-subprocess-run-for-60-sec

> If you just want a program that does this, and it doesn't have to be
> in Python, you might try
> http://stromberg.dnsalias.org/~strombrg/maxtime.html
> It's in C, and is the product of considerable real-world use.  It
> exits almost immediately after its subprocess exits, FWIW.


--
Akira