kick day-old ssh connections

kick.sh

#!/bin/bash

# kick_idle_ssh.sh
# Hangs up ssh connections that have been idle for over a day.
#
# AUTHOR: shwang 2015.11.4


MAX_IDLE_TIME=86400

# `who` only displays login sessions (thus excluding tmux/screen sessions).
# It's pretty safe to assume that on bastions, all sessions listed by `who`
# are ssh connections.
who | tr -s ' ' | while read entry; do
    user=$(echo $entry | cut -d' ' -f1)
    tty=$(echo $entry | cut -d' ' -f2)
    ((idletime = "$(date "+%s")" - "$(stat --format="%X" "/dev/${tty}")" ))

    if ((idletime > MAX_IDLE_TIME)); then
        pid=$(ps -u "$user" | grep -i "$tty" | head -1 | tr -s ' ' | cut -d' ' -f1)
        echo 'You exceeded idle time of 24 hours.' | write $user $tty
        kill -HUP $pid  # hangup the ssh connection
    fi  
done