how do you check if your child process from fork still alive or not? In perl I can send kill(0, $cid), I think. But Process.kill(0, child_id) always returns 1.
To be honest, I couldn't get the perl code to work either. It always returns 1 too.
I can do `ps -p #{child_id}` but I wonder if Process.kill should work too.
how do you check if your child process from fork still alive or not? In perl I can send kill(0, $cid), I think. But Process.kill(0, child_id) always returns 1.
To be honest, I couldn't get the perl code to work either. It always returns 1 too.
I can do `ps -p #{child_id}` but I wonder if Process.kill should work too.
On Thu, 1 Mar 2007, Andreas S wrote:
#
# returns true if pid is running, false otherwise
#
def alive pid #--{{{
pid = Integer("#{ pid }")
begin
Process::kill 0, pid
true
rescue Errno::ESRCH
false
end #--}}}
end
alias alive? alive
it should always return 1. it raises if the pid is dead or you do not have
permission to signal the process.
-a
--
be kind whenever possible... it is always possible.
- the dalai lama
Using Process.kill(0, pid) will return 1 as long as the process exists. In
your situation, I'm guessing that the child process has terminated
but continues to exist as a zombie process. You have to call Process.wait
to reap the child process in order for the child process to disappear entirely.
pid = fork { sleep(10) }
puts Process.kill(0, pid) # 1
sleep 15
puts Process.kill(0, pid) # 1, process is a zombie at this point
Process.wait
puts Process.kill(0, pid) # exception, process doesn't exist
Gary Wright
···
On Feb 28, 2007, at 5:17 PM, Andreas S wrote:
how do you check if your child process from fork still alive or not? In perl I can send kill(0, $cid), I think. But Process.kill(0, child_id) always returns 1.
To be honest, I couldn't get the perl code to work either. It always returns 1 too.
I can do `ps -p #{child_id}` but I wonder if Process.kill should work too.
You have to call Process.wait to reap the child process in order for the child process to disappear entirely.
Gary Wright
I don't want to use Process.wait because it will block. I have a queue that I want to refill with the next job in line when a slot is available. I'm not gaining much from forking jobs like this but my main purpose is to emulate LSF queue on local machine, in case its down or something. By doing so, the rest of the code still sees a queue.
I tried Ara's suggestion, but it doesn't seem to throw exception.
Thanks for such prompt response and I love how Ara, even for merely showing example, gave
alias alive? alive
-andre
def alive pid
pid = Integer("#{ pid }")
begin
Process::kill 0, pid
true
rescue Errno::ESRCH
false
end
end
Hey, that does the trick. Thanks a lot Daniel, and to Gary and Ara.
-andre
···
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