Show EdgeOS DHCP lease table

show-dhcp-leases.sh

#!/bin/bash

# Quickly show the Ubiquity EdgeOS (ie EdgeRouter Lite)
# DHCP leases to identify devices (ie headless raspberrypi)
# without having to go through the EdgeOS web UI.
#
# Thanks to @matthew1471 for API docs
# https://github.com/matthew1471/EdgeOS-API
# requires jq - `brew install jq` on macOS

function detect_gateway_addr {
    case $(uname) in
        Darwin)
            while read -r hw; do
                # the first interface that has a router addr
                gateway=$(networksetup -getinfo "$hw" | awk '/^Router/ { print $2 }')
                [ -n "$gateway" ] && break
            done< <(networksetup -listallnetworkservices)
            ;;
        Linux)
            gateway=$(ip route | awk '/^default/ { print $3 }')
            ;;
        *)
            >&2 echo "Not sure what to do with OS $(uname)"
            ;;
    esac
    
    if [ -z "$gateway" ]; then
        >&2 echo "Unable to figure out your gateway/router address"
        >&2 echo "Trying setting EDGE_DEVICE_ADDR to your gateway's IP address"
        exit 1
    fi
    
    echo $gateway
}

# For the sake of argument here, we're assuming the gateway/router
# is also the DHCP server. Bypass this by setting EDGE_DEVICE_ADDR.
[ -z "$EDGE_DEVICE_ADDR" ] && EDGE_DEVICE_ADDR=$(detect_gateway_addr)

if [ -z "$ERL_USERNAME" ] || [ -z "$ERL_PASSWORD" ]; then
    >&2 echo "set ERL_USERNAME and ERL_PASSWORD env vars"
    exit 1
fi

base_url="https://${EDGE_DEVICE_ADDR}:443"

curl -sk -c $HOME/.erl_cookie ${base_url}/ -d "username=${ERL_USERNAME}&password=${ERL_PASSWORD}" 
json=$(curl -sk -b $HOME/.erl_cookie ${base_url}/api/edge/data.json\?data\=dhcp_leases)

IFS='' read -r -d '' jq_filter <<-'FILTER'
    .output."dhcp-server-leases".LAN1
    | keys[] as $k
    | [
        $k, 
        .[$k].mac,
        .[$k]."expiration",
        .[$k]."client-hostname"
      ]
    | @tsv
FILTER

echo $json | jq -r "$jq_filter"

exit 0