[m-users.] getopt; checking for invalid/illegal option values

[Zoltan Somogyi]

On Sun, 2 May 2021 20:47:29 +0100, "Sean Charles (emacstheviking)" <objitsu at gmail.com> wrote:
> I have a working getopt configuration and, to cut a long story short, is it possible to restrict the values that an option can take or not ?

You can restrict the type, using the option's entry in the option_defaults predicate.
There is no way to disallow any values in that type.

> Essentially I don’t want to the application to start of the command line contains junk.

The standard way to achieve this is to postprocess the option table returned
by getopt. This can e.g. check whether a string option has one of a set of permitted
values (possibly after smashing case), generating an error if not, and recording
the result in an enum that is stored *separately from the option table*, maybe
in the globals structure. It can also do other checks that affect more than one
option, e.g. generating an error if the users sets both a "verbose" option
and a "quiet" option.

Basically, the getopt module has no mechanism built into it for such semantic
checks, because the space of possible semantic checks one may want
is so large.

Zoltan.