mmsh

An experimental CLI parser.

What's inside?

A command prompt built on top of GNU Readline, and a command parser that outputs a data structure that can be used to run the commands entered.

A simple example

If you were to type the following into mmsh:

$ foo < bar | baz > fizz.txt

... it would be interpreted in the following way:

• Run command foo, getting its input from bar
• Run command baz, whose input came from the output of foo
• Write the output of baz to fizz.txt

an IRB session

 > Mmsh.parse(Mmsh.read('>'))
 > foo < bar.input | baz > fizz.output
=>
[#<struct Mmsh::Cmd
  id="d2e22c61-8b93-4e24-bd7a-079b50430060",
  name="foo",
  args="",
  input="bar.input",
  output="d2e22c61-8b93-4e24-bd7a-079b50430060">,
 #<struct Mmsh::Cmd
  id="4140c384-eac8-4fad-9c4f-0bb8b1862a9d",
  name="|",
  args="",
  input=nil,
  output="4140c384-eac8-4fad-9c4f-0bb8b1862a9d">,
 #<struct Mmsh::Cmd
  id="5fe10da0-1b9a-4619-adcb-a231602daa27",
  name="baz",
  args="",
  input="d2e22c61-8b93-4e24-bd7a-079b50430060",
  output="fizz.output">]

Why build this?

I've been working on a few fun side projects lately built around a basic shell, but not requiring a full OS under it. mmsh is my attempt at building just the CLI part.

The execution of the commands parsed is inteded to be run by something else -- anything else that can interpret the data structure that mmsh creates.

The parts

The code in mmsh is made up of relatively few parts:

Command execution

• A Reader that reads your commands from the command line
• A Parser that parses the command(s) you type in, into a simple data structure that can the be executed (or run)