#!/bin/bash
# Get a list of PIDs and their start times and pair them using a
# comma
PID_LIST=$(ps -ef | awk '{print $2 "," $5 }')
# Save the current time as seconds since the epoch
current_time=$(date +"%s")
# Calculate four hours before the current time
four_hours_ago=$(expr $current_time - $(expr 4 \* 60 \* 60))
# For each (PID,start time) pair
for item in $PID_LIST ;
do
    # If this is not the first line
    if ! [[ $item =~ "PID" ]] ; then
        # Convert the pair into an array
        pair=(${item/,/ })
        # Pull out the PID
        pid=${pair[0]}
        # Pull out the start time
        start_time=${pair[1]}
        # Get the start time as seconds since the epoch
        start_secs=$(date -d $start_time +"%s")
        # If the start time is greater than or equal to four hours
        # before now
        if (( $start_secs >= $four_hours_ago )) ; then
            # Do some useful work with the information
            echo "Killing $pid that started at $start_time" ;
        fi ;
    fi ;
done