On May 21, 1:27 pm, bukzor <[EMAIL PROTECTED]> wrote:
> On May 21, 12:13 pm, Roy Smith <[EMAIL PROTECTED]> wrote:
>
>
>
> > In article
> > <[EMAIL PROTECTED]>,
>
> > bukzor <[EMAIL PROTECTED]> wrote:
> > > Does anyone have a pythonic way to check if a process is dead, given
> > > the pid?
>
> > > This is the function I'm using is quite OS dependent. A good candidate
> > > might be "try: kill(pid)", since it throws an exception if the pid is
> > > dead, but that sends a signal which might interfere with the process.
>
> > > Thanks.
> > > --Buck
>
> > The canonical way is to do kill(pid, 0). If it doesn't throw, the process
> > exists. No actual signal is sent to the process either way.
>
> > Of course, the process could exit immediately after the kill() call, so by
> > the time you find out it's alive, it's dead. Such is life.
>
> Thanks! That's exactly what I was looking for. A little more
> background:
>
> "If sig is 0 (the null signal), error checking is performed but no
> signal is actually sent. The null signal can be used to check the
> validity of pid."
>
> Taken from :http://www.opengroup.org/onlinepubs/009695399/functions/kill.html
Here are the functions I wrote with this information. There are three
functions:
kill() is similar to os.kill, but returns True if the pid is dead and
throws less exceptions
dead() checks if a process is dead, and gets rid of zombies if
necessary
goodkill() kills a pid by sending gradually harser signals until dead.
def kill(pid, signal=0):
"""sends a signal to a process
returns True if the pid is dead
with no signal argument, sends no signal"""
#if 'ps --no-headers' returns no lines, the pid is dead
from os import kill
try: return kill(pid, signal)
except OSError, e:
#process is dead
if e.errno == 3: return True
#no permissions
elif e.errno == 1: return False
else: raise
def dead(pid):
if kill(pid): return True
#maybe the pid is a zombie that needs us to wait4 it
from os import waitpid, WNOHANG
try: dead = waitpid(pid, WNOHANG)[0]
except OSError, e:
#pid is not a child
if e.errno == 10: return False
else: raise
return dead
#def kill(pid, sig=0): pass #DEBUG: test hang condition
def goodkill(pid, interval=1, hung=20):
"let process die gracefully, gradually send harsher signals if
necessary"
from signal import SIGTERM, SIGINT, SIGHUP, SIGKILL
from time import sleep
for signal in [SIGTERM, SIGINT, SIGHUP]:
if kill(pid, signal): return
if dead(pid): return
sleep(interval)
i = 0
while True:
#infinite-loop protection
if i < hung: i += 1
else:
print "Process %s is hung. Giving up kill." % pid
return
if kill(pid, SIGKILL): return
if dead(pid): return
sleep(interval)
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