Janetsh - A new system shell

Janetsh

A new system shell that uses the Janet programming language for high level scripting while also supporting the things we love about sh.

Minimal knowledge of janet is required for basic shell usage, but know that as you become more familiar with janet, your shell will gain the power of:

• A powerful standard library.
• Functional and imperative programming.
• Powerful lisp macros.
• Runtime loadable extension modules written in C/C++/rust/...
• Coroutines and exceptions.
• Much much more.

Examples

Basic shell usage

Functional programming

Command capture

Subshells

Demo script

The script that generated these demos

Reference Documentation

Hopefully in the future this sparse reference set will become more polished, but for now the following snippets may help advanced users play with the shell in it's current state.

Job control

A list of running jobs can be found in the variable sh/jobs, each of which is a janet table containing the current state of a user job/pipeline.

The sh package has some functions for manipulating jobs, such as putting them in the foreground, or terminating them. This is not a stable interface for now, so you will need to read the code yourself for documentation.

Some examples:

vim
...
Ctrl+Z
$ (sh/make-job-fg (first sh/jobs))
...
Ctrl+Z
$ sleep 60 &
$ (sh/terminate-all-jobs)

Installation

Currently janetsh is only suitable for experienced developers, in the future it can be packaged in a friendly way.

It requires janet installed from source and a library called linenoise for terminal input, for most people reading "build.sh" and customising it for your system is the only way to build it.

Better instructions coming soon...

Janetsh Internals

Internally janetsh is implemented as a low level C library for the janet programming language, a janet library and a small launcher that does some necessary setup/teardown.

The janet main implementation is a set of janet functions and macros that perform shell job control, control user input and manage your command pipelines.

At the highest level the user is presented with an interactive repl interface which implicitly invokes a janet macro to give janet the familiar sh syntax. You can escape this implicit macro by prefixing a line with '(' which reverts to regular janet mode.

Technically janetsh can be used as a plain janet library, but some care is required as it the library deals with some global resources such as signal handlers and terminals which cannot be shared within a program.

Project Status and Donations

The project is at the proof of concept phase and is only usable by people brave and willing to fix things for themselves.

The author would love donations or help from fellow developers to keep things going forward. Donations will go towards living expenses while developing janetsh and providing upstream support for the janet programming language issues that affect Janetsh.

Donate here via paypal

At your request with each donation leave a message and if appropriate, it will be included below.

Sponsors

You - Your message

Authors

This project is being built with care by Andrew Chambers.

Special thanks to Calvin Rose for creating the Janet programming language.