Simple script to shutdown after SSH iddle.

shutdown-after-idle.sh

#!/bin/bash

IDLE_SSH_CONNECTIONS=$(cat .shutdown-counter)
QUANTITY_OF_CONNECTION=$(who | wc -l)

echo "Idle: $IDLE_SSH_CONNECTIONS"
echo "Who logged: $QUANTITY_OF_CONNECTION"

if [ $IDLE_SSH_CONNECTIONS -gt 30 ]; then
  echo 0 > .shutdown-counter
  echo 'Shutdown executed'
  sudo shutdown now
elif [ $QUANTITY_OF_CONNECTION -gt 0 ]; then 
  echo 'Reseting shutdown counter'
  echo 0 > .shutdown-counter
else
  echo 'Adding 1 minute to iddle time.'
  echo $(expr $IDLE_SSH_CONNECTIONS + 1) > .shutdown-counter
fi

One Line solution:

if [ $(cat .shutdown-counter) -gt 30 ]; then echo 0 > .shutdown-counter; sudo shutdown now; elif [ $(who | wc -l) -gt 0 ]; then echo 0 > .shutdown-counter; else echo $(expr $(cat .shutdown-counter) + 1) > .shutdown-counter; fi;