#!/bin/sh set -eu readonly DHCPD_CONF_FILE="${DHCPD_CONF_FILE:-/etc/dhcpd.conf}" readonly DHCPD_LEASES_FILE="${DHCPD_LEASES_FILE:-/var/db/dhcpd.leases}" DHCPD_CONF_FILE_AWK_SCRIPT=$(cat << 'EOF' /^[ \t]*host[ \t]+[^ \t]+[ \t]+\{[ \t]*$/ { ip = "" hostname = $2 next } /^[ \t]*fixed-address[ \t]+([0-9]{1,3}\.){3}[0-9]{1,3}[ \t]*;[ \t]*$/ { ip = substr($2, 1, length($2)-1) next } /\}/ { if (hostname && ip) { print hostname "\t" ip } hostname = "" ip = "" next } EOF ) readonly DHCPD_CONF_FILE_AWK_SCRIPT DHCPD_LEASES_FILE_AWK_SCRIPT=$(cat << 'EOF' function parse_datetime(datetime) { command = "date -j -f \"%w %Y/%m/%d %H:%M:%S %Z;\" +%s \"" datetime "\"" if (command | getline unix_time < 0) { exit 1 } close(command) return unix_time } /^[ \t]*lease[ \t]+([0-9]{1,3}\.){3}[0-9]{1,3}[ \t]+\{[ \t]*$/ { ip = $2 next } /^[ \t]*(starts|ends)[ \t]+[0-6][ \t]+[0-9]+\/[0-9]+\/[0-9]+[ \t]+[0-9]+:[0-9]+:[0-9]+([ \t]+[a-zA-Z0-9]+)?[ \t]*;[ \t]*$/ { if ($1 == "starts") { $1 = "" # remove the leading space caused by setting $1 to "" starts = parse_datetime(substr($0, 2)) } else { $1 = "" # remove the leading space caused by setting $1 to "" ends = parse_datetime(substr($0, 2)) } next } /^[ \t]*(client-)?hostname[ \t]+\"[^\"]+\"[ \t]*;[ \t]*$/ { hostname = gensub("\"|;", "", "g", $2) next } /^[ \t]*abandoned[ \t]*;[ \t]*$/ { abandoned = 1 next } /\}/ { now = systime() if (!abandoned && hostname && ip && starts && ends && now >= starts && now < ends) { print hostname "\t" ip } hostname = "" ip = "" starts = 0 ends = 0 abandoned = 0 } EOF ) readonly DHCPD_LEASES_FILE_AWK_SCRIPT ( awk "${DHCPD_CONF_FILE_AWK_SCRIPT}" "${DHCPD_CONF_FILE}" awk "${DHCPD_LEASES_FILE_AWK_SCRIPT}" "${DHCPD_LEASES_FILE}" ) | sort -u | column -c 2 -t