Wake on LAN magic packet dispatch implemented in bash

wol.sh

#!/usr/bin/env bash
#
# Wake on lan
#
#  Send WoL magic packet over UDP
#
#  Usage:
#
#    wol MAC ADDRESS [PORT]
#    wol FILE
#
#  Examples:
#
#    wol 01:02:03:04:05:06 192.168.0.255 7    # Send magic packet to 01:02:03:04:05:06
#                                             # via UDP broadcast to 192.168.0.255, port 7
#
#    wol 01:02:03:04:05:06 192.168.0.255      # Send magic packet to 01:02:03:04:05:06
#                                             # via UDP broadcast to 192.168.0.255, port 9
#                                             # (dicard protocol port)
#
#    wol file.wol                             # Send magic packet to MAC in file.wol
#                                             # via UDP broadcast to address in file.wol, port
#                                             # in file.wol (defaults to 9)
#
#  Format of FILE: MAC ADDRESS PORT
#
#  Magic packet structure: https://en.wikipedia.org/wiki/Wake-on-LAN#Magic_packet
#

# Parse args
local mac=
local addr=
local port=
if [[ -e $1 ]]; then
	mac=$(awk '//{print $1}' $1)
	addr=$(awk '//{print $2}' $1)
	port=$(awk '//{print $3}' $1)
else
	mac=$1
	addr=$2
	port=$3
fi
port=${port:-9}						# Default to unofficial WoL UDP port (9)

# Append header bytes (6 * 0xFF) to magic packet payload
local magic=""
local header="\xFF"
for i in {1..6}; do
	magic+=$(echo -en ${header})
done

# Concatenate MAC bytes (16 * MAC) to magic packet payload
mac=${mac//:/}
for i in {1..16}; do
	for ((nibble=0; nibble<${#mac}; nibble+=2)); do
		magic+=$(echo -en "\x${mac:$nibble:2}")
	done
done

# Send magic packet
echo -en ${magic} | nc -Nub -w 0 ${addr} ${port}