Marko Rauhamaa (2016-03-19 14:02 +0300) wrote:
> Alex Kost <[email protected]>:
>
>> Hello, in the guile REPL I evaluated the following:
>>
>> (with-output-to-port (%make-void-port "w")
>> (lambda () (display "foo") (newline)))
>>
>> and I got no output as expected. Then I tried the following:
>>
>> (with-output-to-port (%make-void-port "w")
>> (lambda () (system* "ls" "/tmp")))
>>
>> but there was an output from "ls" command. So my question is: how to
>> get rid of this output?
>
> When you use ports (which the operating system knows nothing about),
> Guile needs to actively jockey the data between them.
>
> (use-modules (ice-9 popen))
> (with-output-to-port (%make-void-port "w")
> (lambda ()
> (let ((output (open-input-pipe "ls /tmp")))
> (let loop ()
> (let ((c (read-char output)))
> (if (not (eof-object? c))
> (begin
> (write-char c)
> (loop)))))
> (close-input-port output))))
Ah, thanks! I get it. But I also want to check an exit status of the
running command (sorry, that I didn't mention it). So I would like to
have the following procedure:
(define (system-no-output* . args)
"Like 'system*' but suppress the output of the command indicated by ARGS."
???)
Or even better (it would be a perfect solution for me) the following macro:
(define-syntax-rule (with-no-process-output body ...)
"Run BODY and suppress all output of the executed sub-processes."
???)
So that I could do something like this:
(with-no-process-output
(let ((status1 (system* "ls" "/tmp"))
(status2 (system* "ls" "/foo")))
(format #t "Very useful info: ~a, ~a~%" status1 status2)))
and there would be no standard/error output from both "ls" calls. Is it
possible?
--
Alex
