[racket] Embedding multiline shell scipts

From: Manfred Lotz (manfred.lotz at arcor.de)
Date: Sun Feb 6 09:26:08 EST 2011

On Sun, 6 Feb 2011 16:06:19 +0200
"Jukka Tuominen" <jukka.tuominen at finndesign.fi> wrote:

> So, once i have created the script within racket as multiline string,
> how do I actually run it within racket without writing or reading any
> external files, and capture the output of the script for further
> processing (also in racket).
> In other words, I could write the script into a file and run it with
> system/output, but how to do it without an external file?

Hmmm, one possibility might be to use process which nicely captures
output. process is especially good if you have a large amount of output
as you can process the output (e.g. write it to a log file) line by

Example: Here the output of the command(s) will just be echoed to
stdout and to stderr. 

(define (print-output in)
      (let loop ((line (read-line in)))
        (if (eof-object? line)
            (begin (printf "~a~n" line)
                   (loop (read-line in))))))

(define shell-cmd
      (lambda (cmd)
        (printf  "~a~n" cmd) ;echoing the cmd which could be omitted
        (let* ([p (process cmd)]
               [stdout (first p)]
               [stdin (second p)]
               [stderr (fourth p)]
               [ctrl (fifth p)])
          (print-output stdout)
          (print-output stderr)
          (close-input-port stdout)
          (close-output-port stdin)
          (close-input-port stderr))))

(define test-cmd "


(shell-cmd test-cmd)

I don't know how to merge stdout and stderr in proper sequence. People
who know racket better than me may interfere to improve my example.


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