local args = { ... }

local modtimes = {}

if #args == 0 then
    print("usage: runonchange [files to watch ...] -- program [args...]")
    return
end

while #args > 0 do
    local name = table.remove(args, 1)
    if name == "--" then break end
    modtimes[name] = -1
end

if #args == 0 then
    printError("No executable was given")
    return
end

while true do
    local shall_run = false
    for name, modtime in pairs(modtimes) do
        local modtime_new = fs.attributes(name).modified
        if modtime_new ~= modtime then
            shall_run = true
            modtimes[name] = modtime_new
            print(name .. " was modified")
        end
    end
    if shall_run then
        local succ, err = pcall(shell.run, table.unpack(args))
        if succ then
            print("Process finished successfully")
        else
            printError("Process crashed: " .. err)
        end
    end
    os.sleep(0.5)
end