How to run shell command with stream input, to get string output

[Jean Louis <bugs@gnu.support>]

Hello,

I would like to know how to make in Emacs Lisp the
equivalent function to what I have here below in
Common Lisp.

I wish to feed a string as stream to a command and
to get the string output.

For example, I would like to do something like
this:

(setq output
      (shell-command-feed-string "markdown" "Hello\n=====\n\n"))

output would then be something like "<h1>Hello</h1>"

so to receive the string back as result from
markdown parsing.

This type of function then I would use on various
commands, not just markdown, but that maybe one
good example.

I have tried searching for similar in Emacs Lisp
manual, could not find it.

With CLISP Common Lisp implementation:

(defun slurp-stream-io-command2 (command string)
  "Returns the output of a command to which string
has been fed, very usable for markdown, emacs Org
mode processing and similar"
  (let* ((stream (make-pipe-io-stream command :external-format "utf-8"))
         (in (two-way-stream-input-stream stream))
         (out (two-way-stream-output-stream stream))
         (result ""))
    (princ string out)
    (finish-output out)
    (close out)
    (setf result (with-output-to-string (var)
		   (loop for c = (read-char in nil)
		      while c
		      do (format var "~A" c))))
    (finish-output in)
    (close in)
    (close stream)
    result))

Thank you,
Jean