Coming from OpenComputers

Modular Computers is OpenComputers’ idea built again, but its computers run mcos, a Linux-like OS, so the way you do things is Linux’s. This page maps what you knew in OpenComputers to how it’s done here. Where something has no equivalent, it says so.

The bus, not components

OpenComputers called a computer’s parts and attached blocks components. Here they’re devices, on the computer’s bus (see the bus), and mcos shows each as a file in /dev, named by kind and number: robotics0, storage1, field0.

With the devices library, a device works as a proxy did:

local devices = require("devices")
local robot = assert(devices.open("robotics0"))
robot.walk(3)
for name, method in pairs(robot) do
  print(name, method)       -- every method, and what it does
end

Every device’s methods are listed in the game too: ls /sys/class/robotics/robotics0/methods, and cat one for what it does.

Signals are files you wait on

OpenComputers queued signals that a program pulled with event.pull. mcos has no signal queue: a device’s news is its /dev file’s, and a program waits for files with sys.poll, as Linux’s poll. One wait can cover devices, the keyboard (standard input), sockets and timers at once.

Waiting for a device to arrive (component_added)

In OpenComputers you’d pull component_added until the right type came. Here a device joining the bus makes its file appear in /dev, and inotify, Linux’s file change notices, says so: CREATE /dev/charger0. devices.wait does that for you, and a device already there counts, so there’s no race between looking and waiting:

local devices = require("devices")
print("waiting for a charging pad to be cabled up...")
local name = devices.wait("charger")
print("found " .. name)

Done by hand, with the same calls any file watcher uses:

local sys = require("sys")

local watch = sys.inotify()
sys.watch(watch, "/dev")
while true do
  sys.poll({[watch] = {IN = true}})
  local notice = sys.read(watch, 4096)        -- "CREATE /dev/charger0"
  local name = notice:match("CREATE /dev/(charger%d+)")
  if name then
    print("found " .. name)
    break
  end
end

A device leaving the bus is DELETE /dev/charger0 (OpenComputers’ component_removed).

Screens are terminals

OpenComputers’ GPU drew characters and colors with calls. A screen here is a VT102/xterm terminal: a program writes text and escape sequences, as on any Linux terminal (see the terminal).

Files and disks

There’s no filesystem component: disks are mounted as directories (the boot disk at /, others at /mnt/sata/1, /mnt/id/...), and files are Lua’s io and the fs and sys libraries. df and mount show the disks. Labels are label.

Networking

OpenComputers’ modem sent messages on ports. Here network cards carry UDP and TCP sockets (sys.socket, sys.sendto, sys.connect; see networking), and rsh and rcp run commands and copy files between computers. A wake message is a card’s method, setWake, on its /dev file. The internet card is wget, curl, or the http library.

Robots

The bot golem’s moves are its robotics device’s methods, and each move ends in an event, so a program waits for it rather than blocking in the call:

Running programs