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Re: How do you record output of both STDERR and STDIN to a string?
From: |
Roel Janssen |
Subject: |
Re: How do you record output of both STDERR and STDIN to a string? |
Date: |
Thu, 10 Sep 2020 17:04:22 +0200 |
On Thu, 2020-09-10 at 04:14 +0300, Bonface M. K. wrote:
> Hi all. Is there a way to "record" the output from both *stderr* and
> *stdout* from a guile process if you wrap it around a "system" call
> to a
> string? Here's something that works. It's not /exactly/ what I want
> because "open-input-pipe" runs the command in a subprocess.
>
> --8<---------------cut here---------------start------------->8---
> (define (run-job job)
> (let* ((port (open-input-pipe job))
> (str (read-line port)))
> (close-pipe port)
> str))
>
> (display (format #t "~s ~s ~s"
> "padding"
> (run-job "echo hello")
> "testing"))
> --8<---------------cut here---------------end--------------->8---
>
> I've tried out creating a fork:
>
> --8<---------------cut here---------------start------------->8---
> (define (run-job thunk)
> (call-with-output-string
> (λ (port)
> (match (pipe)
> ((in . out)
> (match (primitive-fork)
> (0 ; child
> (close in)
> (with-error-to-port out thunk))
> ((= waitpid (pid . exit-code)) ;; parent
> (close out)
> (display (read-line in) port))))))))
>
> ;; Doesn't work:
> (display (format #t "~s ~s ~s"
> "padding"
> (run-job (system "echo hello"))
> "testing"))
> --8<---------------cut here---------------end--------------->8---
>
> Ideally for a correct output without errors, I'd like to have as
> output:
>
> --8<---------------cut here---------------start------------->8---
> "padding" "hello" "testing"
> --8<---------------cut here---------------end--------------->8---
>
> and in the event I have an error, like say, by running (system
> "echoooo hello"), I get
> the output:
>
> --8<---------------cut here---------------start------------->8---
> "padding" "sh: command not found" "testing""
> --8<---------------cut here---------------end--------------->8---
>
> PS: I'm new to Guile :)
>
Having spent a day on this myself, this is the best I had come up with:
--8<---------------cut here---------------start------------->8---
(define (virtuoso-isql-query query)
"Executes QUERY via ISQL and returns a both an ERROR-PORT and a PORT
to read CSV output from."
(let* ((tmp (getenv "TMPDIR"))
(error-port (mkstemp! (string-append (if tmp tmp "/tmp") "/sg-
XXXXXX")))
(port (open-input-pipe
(format #f "~a ~a -U ~a -P ~a verbose=off
csv_rfc4180=on csv_rfc4180_field_separator=, exec='~:a' 2> ~a"
(isql-bin) (isql-port) (rdf-store-
username)
(rdf-store-password)
(string-append "SPARQL " query)
(port-filename error-port)))))
(setvbuf port 'block 4096)
(values error-port port)))
--8<---------------cut here---------------end--------------->8---
I certainly hope someone can come up with a better solution!
Kind regards,
Roel Janssen