Identifying job on a node

Sometimes may happens that on one node you have more than one job running and only one among them you need to kill. How find which one it is? Here is an explanation given by Catherine:

 Get the pids of the candidate processes and examine their open files, which are kept in /proc/<pid>/fd on given node. 
 Do an 'ls -l' on that directory for each pid, which will show you the open files, and see which one has that file open.