Journal

A Portable Bash Function to List Process Hierarchies

It can be useful to find the process hierarchy of a particular process when diagnosing a problematic machine. Say for instance you run into a rogue program and want to find out what spawned it before you kill it. The Unix command pstree (or ptree on Solaris) will show you a tree of running processes but is not always available.

Since I ran into this problem recently, I concocted the following recursive function to traverse a process tree to its root from a given pid:

parents(){ :(){                                                                                                                       
          read p n <<<`ps -o ppid,comm -p $1 | awk 'NR>1{print $1,$2}'`;
          echo -e "$1\t$n";
          test $1 -ne 0 && : $p; };
      : $1; }

Let's see it in action:

stevechallis:~$ parents 28311                                                                                                         
28311   /bin/sh
488 /Applications/Emacs.app/Contents/MacOS/Emacs
1   /sbin/launchd
0

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