On Tue, 22 Feb 2022, Leo Butler <leo.butler@umanitoba.ca> wrote:
Olivier Dion via General Guile related discussions <guile-user@gnu.org>
writes:
On Tue, 22 Feb 2022, Zelphir Kaltstahl <zelphirkaltstahl@posteo.de> 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)
I use the following:
(define-module (shell utils)
#:use-module (ice-9 format)
#:use-module (ice-9 popen)
#:use-module (ice-9 textual-ports))
(define (shell% proc fmt . args)
(let* ((port (open-input-pipe (format #f "~?" fmt args)))
(output (proc port)))
(close-pipe port)
output))
You probably want to inspect the exit value of the shell process, so
that you can handle/throw the error. This is what I use (similar to your
`shell'):
You're absolutely right. It would also probably a good idea to use
dynamic-wind for close-pipe in case an exception is thrown in
read-string I think.
(define* (shell-command-to-string cmd)
(catch 'shell-command-error
;; thunk
(lambda ()
(let* ((port (open-pipe cmd OPEN_READ))
(str (read-string port))
(wtpd (close-pipe port))
(xval (status:exit-val wtpd)))
(if (or (eqv? xval #f) (> xval 0)) (throw 'shell-command-error cmd
str))
str))
;; handler
(lambda (key cmd str)
(simple-format #t "ERROR: in command ~a\nstring: ~a\n" cmd str)
(throw 'error-in-shell-command-to-string cmd str))))
(define-public (shell . args)
(apply shell% (cons get-string-all args)))
(define-public (shell$ . args)
(apply shell% (cons get-line args)))
Then
(shell "ls" "-l")
The $ variant is to get a single line in the output.
I wonder why there is no module already in ice-9 which does this
stuff? It seems like a lot of people are re-inventing the wheel.
There's ton of missing stuffs in the standard library IMO. On top of my
head, filesystem paths manipulation (e.g. path-join) is also one that is
probably getting re-invented a lots.