https://github.com/kindredgroup/revolver

A library for building REPL applications.
https://github.com/kindredgroup/revolver

cli repl shell terminal

Last synced: 4 months ago
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A library for building REPL applications.

• Host: GitHub
• URL: https://github.com/kindredgroup/revolver
• Owner: kindredgroup
• License: mit
• Created: 2022-11-24T22:03:16.000Z (over 3 years ago)
• Default Branch: master
• Last Pushed: 2025-06-18T23:54:14.000Z (about 1 year ago)
• Last Synced: 2026-02-24T20:50:29.805Z (4 months ago)
• Topics: cli, repl, shell, terminal
• Language: Rust
• Homepage:
• Size: 41 KB
• Stars: 0
• Watchers: 8
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
Revolver

===

A library for building REPL applications.

[![Crates.io](https://img.shields.io/crates/v/revolver?style=flat-square&logo=rust)](https://crates.io/crates/revolver)

[![docs.rs](https://img.shields.io/badge/docs.rs-revolver-blue?style=flat-square&logo=docs.rs)](https://docs.rs/revolver)

[![Build Status](https://img.shields.io/github/actions/workflow/status/kindredgroup/revolver/master.yml?branch=master&style=flat-square&logo=github)](https://github.com/kindredgroup/revolver/actions/workflows/master.yml)

[![codecov](https://img.shields.io/codecov/c/github/kindredgroup/revolver/master?style=flat-square&logo=codecov)](https://codecov.io/gh/kindredgroup/revolver)

# Concepts

## Command

The `Command` trait is a specification of an executable command — the 'execute' part of a REPL application. A command will typically be accompanied by a `NamedCommandParser` implementation for converting command strings into `Command` objects.

`Command`s and `NamedCommandParser`s are the only two traits that you must implement. Everything else is just configuration.

### Commander

A `Commander` decodes user input (typically a line read from a terminal interface) into a dynamic `Command` object, using a preconfigured map of `NamedCommandParser`s.

### Built-in commands

Revolver comes with two useful built-in commands that can be used out-of-the-box.

* `help` — A self-help guide, outlining the available commands and how to use them.

* `quit` — Terminates the REPL. (It only exits the loop; it does not terminate the application.)

These commands are opt-in, meaning that you must explicitly include their parsers in your `Commander` to enable them.

## Terminal

The `Terminal` trait represents a text-based interface with the user. It fulfils the 'read' and 'print' parts of a REPL application.

Revolver is currently bundled with two `Terminal` implementations:

* `Streaming` — A terminal device that composes over I/O streams using `Input` and `Output` traits. Out-of-the-box adapters exist for `stdin` and `stdout` streams. Adapters may be written to interface with nonstandard streams by supplying a custom closure.

* `Mock` — A way of mocking a terminal device for feeding input, capturing output, and performing various assertions.

## Looper

`Looper` is a mechanism for iteratively running commands based on successive user input. It fulfils the 'loop' part of a REPL application.

# Getting started

## Add dependency

```sh

cargo add revolver

```

## An example

See [`examples/calculator.rs`](examples/calculator.rs) for a simple calculator REPL.