The Koto CLI

Koto was originally designed as an extension language for Rust applications, but it is also usable as a standalone scripting language via the Koto CLI. The CLI can run .koto scripts, and provides an interactive REPL.


Installing the Koto CLI currently requires the Rust toolchain (see for installation instructions).

With Rust available on your system, run cargo install koto_cli, which provides you with the koto command.

Using the REPL

Running koto without any arguments will start the Koto REPL, where Koto expressions can be entered and evaluated interactively.

> koto
Welcome to Koto 

» 1 + 1
➝ 2

» 'hello!'
➝ hello!


The language guide and the core library reference, can be accessed in the REPL using the help command.

> koto
Welcome to Koto

» help bool


  Booleans are declared with the `true` and `false` keywords, 
  and combined using the `and` and `or` operators.

  |  true and false
  |  # ➝ false