[TUHS] Systematic approach to command-line interfaces

Adam Thornton athornton at gmail.com
Sun Aug 1 00:21:01 AEST 2021

On Jul 31, 2021, at 5:25 AM, Michael Siegel <msi at malbolge.net> wrote:

While doing that, I learned that there is a better way to approach
this problem – beyond using getopt(s) (which never really made sense to
me) and having to write case statements in loops every time: Define a
grammar, let a pre-built parser do the work, and have the parser
provide the results to the program.

I see that Dan Halbert beat me to mentioning "click."

The trick with shell is that unless you write the parser in shell, which is
going to be miserable, you’re doing it in a command in a subshell, and
therefore your return values have to be a structured stream of bytes on
stdout, which the parent shell is going to have to interpret.  An eval-able
shell fragment, where you have a convention of what the variables you get
from the option parser will be, is probably the easiest way, since from the
parent that would look like:

$(parse_my_opts $*)
# Magic variables spring to life
if [ “$OPT_SUBCOMMAND_0” == “burninate” ]; then ….

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