require use of --option=value syntax

[adeschamps]

I'm looking at the follow option of the Unix tail command, and I'm not sure how to implement it. From the help output:

-f, --follow[={name|descriptor}]
                output appended data as the file grows;
                  an absent option argument means 'descriptor'

So the following are equivalent:

$ tail -f some-file
$ tail --follow some-file
$ tail --follow=descriptor some-file

Essentially, I think I need to only accept the = syntax, because in $ tail --follow some-file, some-file should be interpreted as a positional argument (in this case, the name of the file to print) and not as the value for the follow argument (which should default to descriptor). Is this possible?

[kbknapp]

There currently isn't a way to force use of the --option=value syntax. Although, I could add this as an opt-in feature.

You're right that --follow some-file would currently be interpretted as some-file being the value to --follow. There is a way to allow options to have no values (Arg::minimum_values(0)), you'd have to use either $ tail some-file --follow or $ tail --follow -- some-file have it parse correctly in current clap.

I'll add this to the new feature request issues and should be able to knock it out this week.

[adeschamps]

Just wanted to say a very late thank you!