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Re: How do you record output of both STDERR and STDIN to a string?
From: |
Dr. Arne Babenhauserheide |
Subject: |
Re: How do you record output of both STDERR and STDIN to a string? |
Date: |
Thu, 10 Sep 2020 19:48:52 +0200 |
User-agent: |
mu4e 1.4.13; emacs 27.1 |
Roel Janssen <roel@gnu.org> writes:
> 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!
I’m not sure whether it’s better, but this is the solution I found:
(import (ice-9 rdelim) (ice-9 popen) (rnrs io ports))
(define (call-command-with-output-error-to-string cmd)
(let* ((err-cons (pipe))
(port (with-error-to-port (cdr err-cons)
(λ() (open-input-pipe cmd))))
(_ (setvbuf (car err-cons) 'block
(* 1024 1024 16)))
(result (read-delimited "" port)))
(close-port (cdr err-cons))
(values
result
(read-delimited "" (car err-cons)))))
(call-command-with-output-error-to-string "echo 1; echo 2 >&2")
Also available on my website:
https://www.draketo.de/software/guile-capture-stdout-stderr.html
Best wishes,
Arne
--
Unpolitisch sein
heißt politisch sein
ohne es zu merken
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