how to check if ruby script is running in background from PHP script?

say a ruby script is running

ruby.rb SOMEUSERID

using PHP, how can i find out whether something exactly like that is currently running or not ? Currently i am using PID to check but im not sure if this is efficient. What if there are lot of users running the ruby script, and the ruby script unexpectedly closes. The php script now looks for this PID, and then it turns out it's somebody else's ruby script....开发者_JAVA技巧trouble ensues.

I don't like the idea but you can do this on linux

exec('ps -A | grep ruby.rb', $output);

not sure what's about other systems.

Parse output from 'ps ax' perhaps