Bash script for checking internet connection status and keeping a local log when it changes. Meant to be run at some regular interval as a cron job.

icheck.sh

#!/bin/bash
# check internet connectivity status
#   file 'status' contains last known status (online or offline)
#   file 'status.log' has an entry every time status changes

source ./status
echo "last status: $status at $time"
if nc -zw1 google.com 443; then
    echo "online"
    if [[ "$status" = "online" ]]; then
        exit 0
    fi
    echo "we are back"
    status="online"
else
    echo "offline"
    if [[ "$status" = "offline" ]]; then
        exit 0
    fi
    echo "we are down!"
    status="offline"
fi

# if we're here, it means status has changed
tm=$(date +%s)
dt=$(date -R)

cat > status <<EOF
status=$status
time=$tm
EOF

delta=$((tm-time))
echo "$status at $dt ($delta seconds)" >>status.log