Portable shell solution to check if PID is zombied

Question

I want to check if a PID is running (that is, exists and is not zombied).

It's really quick to do from /proc/$PID/stat but I'd like something more portable.

The best I have right now is:

( STAT="$(ps -ostat= -p$PID)"; test "$STAT" -a "$STAT" "!=" "Z" ) 

Which seems to work on BSD and Linux. Is there a better way?

Answer 1

Hopefully POSIX compliant. Tested with dash. To use it, save it with your favorite editor, make it executable (chmod 755 foo.sh), and run it with a PID argument.

Of course you can adapt it as needed.

#!/bin/sh pid="$1"; psout=$(ps -o s= -p "$pid"); pattern='[SRDTWX]';  case "$psout" in      $pattern) echo "Not a zombie";;     Z) echo "Zombie found";;     *) echo "Incorrect input";;  esac