Re: What is the output port of `system*'?

["Diogo F. S. Ramos" <dfsr@riseup.net>]

> "Diogo F. S. Ramos" <dfsr@riseup.net> writes:
>
>> The following program doesn't output to a string, which I expected.
>>
>> (define foo
>>   (with-output-to-string
>>     (lambda ()
>>       (system* "ls" "/tmp"))))
>
> As the manual says about `system*':
>> The command is executed using fork and execlp.
>
> That implies certain restrictions.  See (ice-9 popen), documented in
> (info "(guile) Pipes").  That also spawns a process but sets its stdout
> to a Unix pipe for which it gives you a Guile port, from which you can
> drain the output to construct a string.

Thanks for the pipe reference.

Indeed, something can probably be written with these pipes to achieve
what my sample program tried to do tho the higher issue remains.

> (Details: `with-output-to-string' could be said to work by setting the
> current output port to some special value (a "string port" I guess) that
> tells the deepest Guile IO procedures to construct a string instead of
> writing to a file descriptor; when you spawn a separate process you
> obviously lose this ability, the spawned process simply inherits the
> current stdout file descriptor of the Guile process and writes to that.)

I'm not sure about the underlying implementation, but I expected all
output to (current-output-port) going to the resulting string, hence my
question.

As an example of this behavior, I point to the following Racket program:

--8<---------------cut here---------------start------------->8---
#lang racket

(define foo
  (with-output-to-string
    (lambda ()
      (system* (find-executable-path "ls") "/tmp"))))
--8<---------------cut here---------------end--------------->8---