CoffeeScript shell language. Like Bash, but Cash.
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Cash (WIP)

CoffeeScript shell language. Like Bash, but Cash.

Bash (like most other shell languages) is fantastic at working with files and processes. It (like most other shell languages) sucks in most other language features, particularly syntax and control flow.

CoffeeScript is a fantastic language (better than most other high-level programming languages), particularly in syntax and control flow. It (like most other high-level programming languages) sucks at working with files and processes. [1]

We can't change the language features of Bash, but we can add convenience APIs to CoffeeScript. And thus, Cash was born.

This is a work in progress, starting from scratch. Follow along, submit your feature ideas, contribute code, or just spread the word.


(All instances of "would" below are shorthand for "could/should/would".)

What a hello-world Cash script might look like:

#!/usr/bin/env cash

echo 'hello world!'

You'd be writing CoffeeScript, but you'd have access to common shell tools directly in the global namespace. This could be achieved by the cash binary executing some common code before each script, e.g. (in CoffeeScript):

cash = require 'cash'
{echo, ls, cat, …} = # or utils or whatever

As the above example shows, Cash would be a library, too, so that you could use these helpers in regular CoffeeScript code as well, e.g. a Cakefile.

One of Bash's monstrosities differences from high-level scripting languages is how it handles commands' output (redirects them to stdout) vs. their success/error status (returns exit codes). Commands in Cash would always return their output, throwing an error if they failed. (Need to figure out how to pass things to commands that require input from stdin. Are there any?)

This would let you work with I/O like you're used to:

#!/usr/bin/env cash

    echo cat ''
catch err
    echo 'Uh oh, failed to read readme: ', err

The echo cat line is interesting. That's vanilla CoffeeScript, which is nice and normal for regular high-level languages, but that would use piping in Bash: cat | echo. (This is a silly example because echo doesn't use stdin, so help me think of a better but still simple example!)

Unfortunately, supporting the pipe operator wouldn't be trivial, but it might be possible if we parse the CoffeeScript AST and transform pipe operators into the normal chain/wrap syntax above. That might be a cool thing to explore down the line for the < and > redirect operators too. But it's not urgent.

You can see so far though that scripts should "read" synchronously. For a shell script, you definitely don't want to deal with asynchronicity by default. I don't believe Node provides synchronous APIs for shell execution, so either these wrappers would have to be native extensions for Node, or we'd run Cash scripts through Streamline (but that'd require scripts to use _, which would be nice to avoid).


MIT. © 2012 Aseem Kishore.


I've been thinking about this for a while, but a definite hat-tip to the Plumbum project for some inspiration.