Clsh

Clsh is a set of Lispy bindings for running and composing *nix processes.

Rationale

Common Lisp is amazing, but unfortunately sometimes libraries are not present that we need. More often than not, we have access to a command line tool that we can use to perform a given task.

Example

(in-package :clsh-user)

(in-readtable :clsh-syntax)

;; outputs "hello world"
(with-programs ("echo")
  (to *standard-output*
      (echo :arguments '("hello world"))))

;; outputs lines that match "bin"
(with-programs ("ls" "grep")
    (to *standard-output*
        (pipe ls
              (grep "bin"))))

;; outputs computer's hostname
(with-programs ("echo")
   (to *standard-output*
       (echo :arguments (list $HOSTNAME))))

;; creates an environment variable FOO set to "val"
(setf $FOO "val")

;; outputs "val"
(with-programs ("echo")
   (to *standard-output*
       (echo :arguments (list $FOO))))

For more example usage, see example.lisp

CL Extensions

Common Lisp functions can arbitrarily be mixed with shell functions. To do this, one might try something like:

(in-package :clsh-user)

(use-package :unix-streams)

(defun my-outputter (&key stdin arguments)
  (declare (ignore arguments))
  (when (not stdin)
    (error "ERROR missing stdin in call to my-outputter"))
  (loop for x = (read-line stdin nil)
        while x
        do (format t "~a~%" x)
        finally (unix-close (unix-stream-file-descriptor stdin))))

(with-programs ("echo")
  (pipe (echo "hello world")  my-outputter))

This way, it is possible to parse complex data structure (e.g. JSON, etc) returned from external processes.

License and Copyright

Copyright 2018, Maxwell Taylor. Provided under the terms specified in the MIT license.