I've just ported a small sript to Racket to investigate Racket as a
scripting language for cli tasks. (My past Racket experiences have
really only been with the HTDP languages.) I was quite happy with the
process and the results, but I have one question I haven't been able to
figure out on my own:
How can I specify a mandatory argument such that without the argument
the script will stop, possibly with an error, and preferably display the
help?
In the following, I would like to make the "-d" flag non-optional, or
alternatively specify it as a required non-flag argument. Perhaps I just
need to specify it as a non-flag argument and raise my own errors? Or is
there a built-in way that I've not found?
------------------------------------------------------------------------
(define slow-copy
(command-line
#:program "slowcp"
#:usage-help "\n Copy <files> at a limited rate"
#:once-each
[("-t") time "the duration of <time> in seconds between each copy; default:
5"
(copy-delay (string->number time))]
[("-d") dest "the directory to which <files> will be copied; default: ."
(destination dest)]
#:args files
files
))
------------------------------------------------------------------------
» the complete script is here:
» https://github.com/tuirgin/racket-cli/blob/master/slowcp.rkt
Any criticism or pointers towards a more idiomatic implementation are
definitely welcome.
--
Christopher D. Walborn : http://laconic-prolixity.blogspot.com
------------------------------------------------------------------------
1st Gent.: Our deeds are fetters that we forge ourselves.
2nd Gent.: Ay, truly: but I think it is the world
That brings the iron. (Middlemarch, George Eliot)
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