Re: Shell commands with output to string

[Alex Sassmannshausen <alex.sassmannshausen@gmail.com>]

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Hi Zelphir,

I think you want to be using the popen / pipe procedures for this. See
https://www.gnu.org/software/guile/docs/docs-2.2/guile-ref/Pipes.html
for the chapter in the manual.

Hope this helps :)

Alex

Zelphir Kaltstahl <zelphirkaltstahl@posteo.de> writes:

> Corrections below.
>
> On 2/22/22 10:29, Zelphir Kaltstahl wrote:
>> Hello Guile users!
>>
>> How would I run a shell command from inside Guile and get its output
>> as a string, instead of the output being outputted directly? (Guile
>> 3.0.8)
>>
>> So far I have found
>>
>> ~~~~
>> (system ...)
>> ~~~~
>>
>> which I tried to use with
>>
>> ~~~~
>> scheme@(guile-user)> (with-output-to-string
>>   (system "ls -al"))
>>
>> ;; lots of output immediately shown and not stored in variable
>>
>> ice-9/boot-9.scm:1685:16: In procedure raise-exception:
>> Wrong type to apply: 0
>>
>> Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
>> scheme@(guile-user) [1]> ,bt
>> In ice-9/ports.scm:
>>     476:4  2 (with-output-to-string 0)
>> While executing meta-command:
>> In procedure frame-local-ref: Argument 2 out of range: 1
>> ~~~~
>>
>> But this does not give me a string back.
>>
>> I also tried with
>>
>> ~~~~
>> scheme@(guile-user)> (call-with-values (lambda () (system "ls -al"))
>> ... (lambda (exit-code output) output))
>>
>> ;; lots of output immediately shown
>>
>> ice-9/boot-9.scm:1685:16: In procedure raise-exception:
>> Wrong number of values returned to continuation (expected 2)
>>
>> Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
>>
>> scheme@(guile-user) [1]> ,bt
>> In current input:
>>     10:29  1 (_)
>> In ice-9/boot-9.scm:
>>   1685:16  0 (raise-exception _ #:continuable? _)
>> ~~~~
>>
>> Is there another function I should be using?
>>
>> I would like to have the exit code and the output of a command.
>>
>> Best regards,
>> Zelphir
>
> Of course I should use `with-output-to-string` correctly:
>
> ~~~~
> scheme@(guile-user)> (with-output-to-string
>   (lambda () (system "ls -al")))
> ;; directly outputted stuff
> $1 = ""
> ~~~~
>
> But still not a win.
>
> Regards,
> Zelphir


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