How can I check from Ruby whether a process with a certain pid is running?
Solution 1:
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
Solution 2:
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
>>
Solution 3:
@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.