detect and show IP Address, MAC Address and OS of all computers on local network.

awol.sh

#!/bin/sh

# detect and show IP Address, MAC Address and OS of local network computers.
# requires nmap and ip(iproute2).

gateway=$(ip route); gateway=${gateway#*via }; gateway=${gateway%% *}
localip=$(ip route get 1); localip=${localip#*src }; localip=${localip%% *}
scan=$(sudo nmap -sT -n -O --host-timeout 1m "${gateway:?}"/24) || exit 1

printf '%s\n' "${scan:?}" | while IFS= read -r line; do case $line in 'Nmap scan report for '*)
    unset ip mac os maker
    ip=${line##* }
    [ "$ip" = "$gateway" ] || [ "$ip" = "$localip" ] && continue
    while IFS= read -r line; do case $line in
        Skipping*) break ;;
        'MAC Address:'*) line=${line#*: }; mac=${line%% *}; maker=${line#* }; maker=${maker#*(}; maker=${maker%)*} ;;
        'OS details:'*|*'OS guesses'*) os=${line#*: }; os=${os%%,*} ;;
        'Network Distance'*) printf '%s\t%s\t%s\t%s\n' "$ip" "$mac" "$os" "$maker"; break ;;
    esac; done
;; esac; done