[racket] fun with ports and (system ..) calls

You can also simplify the reading in part with port->lines

#lang racket
(define-values (in out) (make-pipe))
(parameterize ([current-output-port out])
  (system (format "find . ~a ~a" "-name \"*.c\"" "-print"))
  (close-output-port (current-output-port))
  (port->lines in))


On Wed, Oct 16, 2013 at 1:36 PM, David Vanderson
<david.vanderson at gmail.com>wrote:

>
> On 10/16/2013 12:35 PM, Vlad Kozin wrote:
>
>> assuming I have a number of .c files I expect "find" to write
>> corresponding lines to (current-output-port). I want to collect them in a
>> list. Here's a solution I thought would work:
>> ------------------------------**------
>> (define-values (in out) (make-pipe))
>> (parameterize ((current-output-port out))
>>    (system (format "find . ~a ~a" "-name \"*.c\"" "-print"))
>>    (for/list ((line (in-lines in)))
>>      line))
>>
>> It doesn't. It blocks expecting input.
>>
>> Blocks again. Am I not getting EOF here?
>>
>>  I think you are on the right track here.  You need to close the output
> port on the pipe so "in-lines" stops reading:
>
>
> (define-values (in out) (make-pipe))
> (parameterize ((current-output-port out))
>   (system (format "find . ~a ~a" "-name \"*.c\"" "-print"))
>   (close-output-port (current-output-port))
>
>   (for/list ((line (in-lines in)))
>     line))
>
> Does that make sense?
>
> Alternatively you can rearrange your last example:
>
> (define str (with-output-to-string
>
>                (lambda ()
>                  (system (format "find . ~a ~a" "-name \"*.c\""
> "-print")))))
> (for/list ((line (in-lines (open-input-string str))))
>   line)
>
> Thanks,
> Dave
>
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