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Hi, I'm querying a list of network servers for processes belonging to a
specific user. The problem is that when I try to read the stdout from the
subprocess it sometimes hangs. Not always though.

I thought maybe I needed to set unbufferered to true, so at the beginning of
the code I set
os.environ['PYTHONUNBUFFERED'] = '1'
But I think it's more likely the subprocess that needs to be unbuffered.

Here's the bit of code:
---------------------------
for machine_name in self.alive:# a list of servers that responded to
ping already.
cmd = ["/bin/remsh", machine_name, 'ps -flu %s' % uid]
finish = time.time() + 4.0
p = subprocess.Popen(cmd,stdout=subprocess.PIPE)
while p.poll() is None:
time.sleep(0.5)
if finish < time.time():
p.kill()
print 'skipping' # this works ok
break

s = ''
if p:
s = p.stdout.read() # trhis will hang occasionally
if not s:
continue
---------------------------

Any ideas? comments on code welcome also.
thanks,
--Tim Arnold

>
> Any ideas? comments on code welcome also.

Here's something that I would probably do, there may be better ways.
This only works on python2.6 for the terminate() method.


import signal
import subprocess

def timeout_handler(signum, frame):
print "About to kill process"
p.terminate()

for machine_name in self.alive:
cmd = ["/bin/remsh", machine_name, 'ps -flu %s' % uid]
signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(1)
p = subprocess.Popen(cmd,stdout=subprocess.PIPE)
(stdout, stderr) = p.communicate()
signal.alarm(0)
if stdout:
print stdout
elif stderr:
print stderr



--
Thanks,
--Minesh

"Minesh Patel" <> wrote in message
news:mailman.1408.1255583431.2807.python-...
> >
>> Any ideas? comments on code welcome also.
>
> Here's something that I would probably do, there may be better ways.
> This only works on python2.6 for the terminate() method.
>
>
> import signal
> import subprocess
>
> def timeout_handler(signum, frame):
> print "About to kill process"
> p.terminate()
>
> for machine_name in self.alive:
> cmd = ["/bin/remsh", machine_name, 'ps -flu %s' % uid]
> signal.signal(signal.SIGALRM, timeout_handler)
> signal.alarm(1)
> p = subprocess.Popen(cmd,stdout=subprocess.PIPE)
> (stdout, stderr) = p.communicate()
> signal.alarm(0)
> if stdout:
> print stdout
> elif stderr:
> print stderr
>
>
>
> --
> Thanks,
> --Minesh

Hi Minesh,
Looks like I need to learn about signals--that code looks nice. I'm using
python2.6.
thanks,
--Tim Arnold