Re: help needed with stderr redirection

[tomas]

On Sat, Oct 22, 2022 at 01:29:05AM +0200, Csepp wrote:
> I have this short snippet of code for a Guix related utility script and
> for the love of the Glowcloud it does not want to work.  I want to
> filter stderr for certain lines and they are not being redirected.  When
> running the full script from a shell, it correctly captures standard
> out, but all the warnings and errors from the subprocess and/or its
> children go directly to the terminal.
> 
> I looked in the Guix sources to see how others do it and found mention
> of a possibly related bug:
> https://debbugs.gnu.org/cgi/bugreport.cgi?bug=52835
> Is that still relevant?  Because debuggs is just, khm, great, I don't
> see any clear indication of what its status is.
> 
> (define (with-input-from-make thunk)
>   (with-error-to-port
>       (current-output-port)
>     (lambda _
>       (with-input-from-port
>           (open-pipe* OPEN_READ "make")
>         thunk))))

I think `with-error-to-port' just directs the error messages of the
current process. Not the ones of the subprocess you are invoking with
open-pipe*. Could that be the case?

To get a better idea of what's going on, you can let a subshell handle
that redirection for you, substitute `open-pipe*' with the star-less
variable and try:

  (open-pipe OPEN_READ "make 2>&1")

If that works as you expect, you can work your way from there. If not,
we've learnt something :)

Cheers
-- 
t

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