Shells provide some sort of a language to interface with the operating system. Unfortunately, they tend to have ugly, and redundant syntax, combined with primitive expressive power. There is little or no typing of the objects manipulated by the shell language, making type errors common. They have entirely missed the developments in language technology of the last 20 years.

In this project you will design and implement a shell. It should be expressive, have clean syntax in the style of Haskell. You should design a simple type system for the language.

• Core requirements:
  • You should implement at least a basic functional shell. This would require the design of a suitable syntax and type system, based on Haskell. The shell, at minimum, should have control constructs, in the style of Haskell.
  • The pipes of a traditional shell may be expressed as function composition, which implies commands should have function type.
  • You shell shouuld certainly be able to provide variables, and file system objects should be values of some kind.
  • Further shell features should be proposed.
• Extra tasks for the ambitious:
  • Your shell should provide fine-grained typing of file system objects.
  • A semantics of job control would be good for the ambitious.
  • You may adapt the composition of shell code and compiled code, in the style of Esther.

• An overview of the Esther shell. And, in significant detail.
• Towards a Strongly Typed Operating System further describes Esther, along with a general approach to typing operating system objects.
• ScSh : The Scheme Shell
• Es, a shell with higher-order functions.
• A very early functional shell, the F shell.
• A simple Haskell shell
• A set of unix utilities providing Haskell list programming in any shell: h4sh
• A unix shell binding in Haskell, of sorts.
• Hashell is a shell written in Haskell and which it is intended to provide a set of abstractions that allows you to use Haskell as a shell programming language.