Snippet for AwesomeRC to "Toggle" a process

gistfile1.lua

toggle_pids = {}
function toggle_process(cmd)
    pid = toggle_pids[cmd]

    if (pid == nil) then
        pid = awful.util.spawn(cmd)
    else
        awful.util.spawn("kill " .. pid)
        pid = nil
    end
    toggle_pids[cmd] = pid
end