_G

Functions in the global environment, defined in bios.lua. This does not include standard Lua functions.

sleep(time)Pauses execution for the specified number of seconds.
write(text)Writes a line of text to the screen without a newline at the end, wrapping text if necessary.
print(...)Prints the specified values to the screen separated by spaces, wrapping if necessary.
printError(...)Prints the specified values to the screen in red, separated by spaces, wrapping if necessary.
read([replaceChar [, history [, completeFn [, default]]]])Reads user input from the terminal.
_HOSTStores the current ComputerCraft and Minecraft versions.
_CC_DEFAULT_SETTINGSThe default computer settings as defined in the ComputerCraft configuration.
sleep(time)Source

Pauses execution for the specified number of seconds.

As it waits for a fixed amount of world ticks, time will automatically be rounded up to the nearest multiple of 0.05 seconds. If you are using coroutines or the parallel API, it will only pause execution of the current thread, not the whole program.

tip

Because sleep internally uses timers, it is a function that yields. This means that you can use it to prevent "Too long without yielding" errors. However, as the minimum sleep time is 0.05 seconds, it will slow your program down.

warning

Internally, this function queues and waits for a timer event (using os.startTimer), however it does not listen for any other events. This means that any event that occurs while sleeping will be entirely discarded. If you need to receive events while sleeping, consider using timers, or the parallel API.

Parameters

  1. time number The number of seconds to sleep for, rounded up to the nearest multiple of 0.05.

Usage

  • Sleep for three seconds.

    print("Sleeping for three seconds")
sleep(3)
print("Done!")

See also

write(text)Source

Writes a line of text to the screen without a newline at the end, wrapping text if necessary.

Parameters

  1. text string The text to write to the string

Returns

  1. number The number of lines written

Usage

  • write("Hello, world")

See also

  • print A wrapper around write that adds a newline and accepts multiple arguments
print(...)Source

Prints the specified values to the screen separated by spaces, wrapping if necessary. After printing, the cursor is moved to the next line.

Parameters

  1. ... The values to print on the screen

Returns

  1. number The number of lines written

Usage

  • print("Hello, world!")
printError(...)Source

Prints the specified values to the screen in red, separated by spaces, wrapping if necessary. After printing, the cursor is moved to the next line.

Parameters

  1. ... The values to print on the screen

Usage

  • printError("Something went wrong!")
read([replaceChar [, history [, completeFn [, default]]]])Source

Reads user input from the terminal. This automatically handles arrow keys, pasting, character replacement, history scrollback, auto-completion, and default values.

Parameters

  1. replaceChar? string A character to replace each typed character with. This can be used for hiding passwords, for example.
  2. history? table A table holding history items that can be scrolled back to with the up/down arrow keys. The oldest item is at index 1, while the newest item is at the highest index.
  3. completeFn? function(partial: string):{ string... } | nil A function to be used for completion. This function should take the partial text typed so far, and returns a list of possible completion options.
  4. default? string Default text which should already be entered into the prompt.

Returns

  1. string The text typed in.

Usage

  • Read a string and echo it back to the user

    write("> ")
local msg = read()
print(msg)

  • Prompt a user for a password.

    while true do
  write("Password> ")
  local pwd = read("*")
  if pwd == "let me in" then break end
  print("Incorrect password, try again.")
end
print("Logged in!")

  • A complete example with completion, history and a default value.

    local completion = require "cc.completion"
local history = { "potato", "orange", "apple" }
local choices = { "apple", "orange", "banana", "strawberry" }
write("> ")
local msg = read(nil, history, function(text) return completion.choice(text, choices) end, "app")
print(msg)

See also

Changes

  • Changed in version 1.74: Added completeFn parameter.
  • Changed in version 1.80pr1: Added default parameter.
_HOSTSource

Stores the current ComputerCraft and Minecraft versions.

Outside of Minecraft (for instance, in an emulator) _HOST will contain the emulator's version instead.

For example, ComputerCraft 1.93.0 (Minecraft 1.15.2).

Usage

  • Print the current computer's environment.

    print(_HOST)

Changes

  • New in version 1.76
_CC_DEFAULT_SETTINGSSource

The default computer settings as defined in the ComputerCraft configuration.

This is a comma-separated list of settings pairs defined by the mod configuration or server owner. By default, it is empty.

An example value to disable autocompletion:

shell.autocomplete=false,lua.autocomplete=false,edit.autocomplete=false

Usage

  • _CC_DEFAULT_SETTINGS

Changes

  • New in version 1.77