Re: [PATCH] Add 'guix hash'.

[Ludovic Courtès]

Nikita Karetnikov <address@hidden> skribis:

>> Ah, TOCTTOU, right.
>
>> You could do:
>
>>   (let ((hash (catch 'system-error
>>                 (lambda ()
>>                   (call-with-input-file ...))
>>                 (lambda args
>>                   (leave (_ "error ..." (strerror (system-error-errno 
>> args))))))))
>>     ...)
>
> Here is what I did (I'll remove "guix hash" when we have "warning"):
>
>       (match args
>         ((file)
>          (catch 'system-error
>            (lambda ()
>              (format #t "~a~%"
>                      (call-with-input-file file
>                        (compose fmt sha256 get-bytevector-all))))
>            (lambda args
>              (leave (_ "~a: ~a~%")
>                     "guix hash" (strerror (system-error-errno args))))))
>         (_
>          (leave (_ "~a: wrong number of arguments~%")
>                 "guix hash")))))

Looks good.

> I guess that "wrong number of arguments" can be handled by
> (lambda args ...).  Still, the above feels much safer.

Not sure what you mean, but the above snippet is OK.

Ludo’.