The Linux and Unix Menagerie: Idle Process Time On Linux And Unix: How To Find It Again

Hey There,

In our final installment on "finding a process's idle time on Linux or Unix," (last touched upon in our post on echo debugging) we looked at whole lot of ways one could go wrong trying to find the idle time of a process on Linux or Unix. This post is a little more upbeat ;)

All of the previous issues with "who -T" have been worked out. Basically, this means that I've gone over it every which way and could find no good reason to use it, as opposed to "w." Of course, in our particular case, we are looking, specifically, for a single process's idle time (as opposed to a user process's idle time; reported by "who -T"). And, although it's a little bit of a pain (initially), short of programming in C (accessing the pstatus struct on Solaris, to be exact - the name and location may vary from distro to distro of proprietary, or free, Unix and/or Linux), linking the pty information from ps with the "idle time" information from w, seems to be the best way to get this information. So far, it's the most efficient way I could find using simple bash scripting.

Attached to today's post is the final "blog" version of this script. It comes with a few notes (possibly of caution) and may need to be modified for your system/OS (There's the first one ;)

The script runs very simply, and you only need to supply it with a PID. You can, optionally, supply a username as a second argument:

host # ./rip 17787

if you just run it with no arguments, you'll get a usage screen, which may or may not help ;)

host # ./rip
Usage: ./rip PID [user]
User defaults to the value
of $LOGNAME if not specified

Please see our previous post on echo debugging this script for more detailed sample output.

I hope you find some good use for this script, and, without further ado, the oft-dreaded notations of explanation ;)

1. This script has been rewritten to be self-contained. Please see the bottom line for any substitute command you may want to use. Actually, making this command a variable might be a good idea. Just call me "Lazy" ;)

2. You can remove the explicit PATH definition if you like. I put it in there specifically to make sure that the "which ps" variable assignment didn't accidentally grab /usr/ucb/ps on Solaris

3. You can comment out the SIGNAL variable as well, since plain old kill is a sig TERM or 15. The only real reason to set this would be if you wanted to always run kill with a different signal (like SIGKILL,, or 9, for example)

4. I changed the minimum idle time to 30 minutes from 45 (in the previous revisions)

5. All variables appearing in this work are fictitious. Any resemblance to real variables, living or dead, is purely coincidental ;)

Cheers,

This work is licensed under a
Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License

#!/bin/bash

#
# rip - Kill any processes that we know have been idle for more than 30 minutes
#
# 2009 - Mike Golvach - eggi@comcast.net
#
# Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License
#
 
PATH="/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin"
procowner="rftprocowner"
prog="\./rft"
sed=`which sed`
awk=`which awk`
ps=`which ps`
grep=`which grep`
kill=`which kill`
signal="-15"

while read a b c d
do
 pid=$b
 pid_not_var=$(echo $pid | $grep [A-z])
 
 if [[ ! -z $pid_not_var ]]
 then
  echo "pid $1 contains non-numeric characters!"
  continue
 fi
 
 pid="$b"
 pid_pty="$c"
 
 if [[ -z "$pid_pty" ]]
 then
  echo "pid $pid is either non-existent, not owned by \"$procowner\" or not attached to a p/tty!"
  continue
 elif [[ "$pid_pty" = "?" || "$pid_pty" = "console" ]]
 then
  echo "pid $pid is not attached to a pty!" # kill OR LEAVE IT?
 else
  pty_num=$(echo "$pid_pty"|$sed 's/^[^\/]*\///')
 fi
 
 proc_time=$(w -sh $procowner|grep $pty_num|grep -v grep|$awk '{if ( $2 == '"$pty_num"' && NF == 4 ) print $3;else if ( $2 == '"$pty_num"' && NF == 3) print "0"}')
 
 proc_is_num=$(echo $proc_time | $grep [A-z])
 if [[ ! -z $proc_is_num ]]
 then
  unset proc_time
 fi
 
 ext_proc_time=$(echo $proc_is_num | $grep [A-z])
 
 if [[ ! -z "$ext_proc_time" && -z "$proc_time" ]]
 then
  echo "killing $pid - $d Up Over 24 Hours: $ext_proc_time $proc_time"
###  $kill $signal $pid
 elif [[ "$proc_time" = "0" ]]
 then
  :
 else
  proc_idle_time=$(echo $proc_time|$grep -v "[:]")
  if [[ -z $proc_idle_time || $proc_idle_time -gt 30 ]]
  then
   echo "killing $pid - $d Up More Than 30 Minutes: $ext_proc_time $proc_time $proc_idle_time"
###   $kill $signal $pid
  fi
 fi
done <<< "`$ps -fu $procowner -o procowner,pid,tty,comm|$grep "$prog"|$grep -v grep`"