The question title says it all. If there is more than one way, please list them. :) I only know of one, but I'm wondering if there is a cleaner, in-Ruby way.
views:
1670answers:
5Note that parsing the output may help tell you if a process has that PID, but it may not be "your" process.
Dustin
2008-11-28 05:21:42
@Dustin: Right. Good point.
Pistos
2008-11-28 05:24:17
Any of the above methods will only tell you if a process exist at a certain PID, not if it is indeed your process.Parsing the various columns of PS output would be a good way of determining with high likelihood if the process is yours.
Douglas F Shearer
2010-05-28 22:51:39
+12
A:
If it's a process you expect to "own" (e.g. you're using this to validate a pid for a process you control), you can just send sig 0 to it.
>> Process.kill 0, 370
=> 1
>> Process.kill 0, 2
Errno::ESRCH: No such process
from (irb):5:in `kill'
from (irb):5
>>
Dustin
2008-11-28 05:17:26
dang, beat me to it.I saw the "new answers have been posted" thing and my heart sank :(
John T
2008-11-28 05:21:51
From my man page: A value of 0, however, will cause error checking to be performed (with no signal being sent). This can be used to check the validity of pid.
Dustin
2008-11-28 05:35:16
Dang, was looking at signals man page, etc. Didn't think to look at kill's manpage. :) Thanks, Dustin.
Pistos
2008-11-28 05:37:11
+2
A:
You can try using
Process::kill 0, pid
where pid is the pid number, if the pid is running it should return 1.
John T
2008-11-28 05:19:38
+7
A:
@John T, @Dustin: Actually, guys, I perused the Process rdocs, and it looks like
Process.getpgid( pid )
is a less violent means of applying the same technique.
Pistos
2008-11-28 05:23:57
A:
The difference between the Process.getpgid and Process::kill approaches seems to be what happens when the pid exists but is owned by another user. Process.getpgid will return an answer, Process::kill will throw an exception (Errno::EPERM).
Based on that, I recommend Process.getpgid, if just for the reason that it saves you from having to catch two different exceptions.
Here's the code I use:
begin
Process.getpgid( pid )
true
rescue Errno::ESRCH
false
end
tonystubblebine
2010-08-25 16:43:41