What are differences between POSIX vi and minimal vi implementations, if any?

Question

I have a few questions about vi and its current relationship with Vim. First of all, is Vim minimal (i.e. the default vi on Cygwin) basically a POSIX compliant implementation of vi? I believe POSIX sets minimum standards and so allows additional features not specified in the standard. Does this common minimal vi implementation have any features not found in the standard? What other common 'minimal' vi's exist?

Secondly, I am aware that there are a lot of differences between vi and Vim. Is there a comprehensive list of how Vim enhances on vi?

Answer 1

is Vim minimal (i.e. the default vi on Cygwin) basically a POSIX compliant implementation of vi?

No. The vi in Cygwin's vim-minimal package still has features not defined by POSIX. I've verified the availability of visual mode and windowing support, for example.

What other common 'minimal' vi's exist?

BSD's nvi is pretty minimal, though it has some features not present in Cygwin's vim-minimal, such as multiple undo.

But if you're looking for a true throwback, I suggest that you look at Heirloom vi.

Is there a comprehensive list of how Vim enhances on vi?

Yes. See the vi_diff section of the user manual. It's also available in the online help via :help vi_diff, though ironically the online help isn't included in Cygwin's vim-minimal package.

Answer 2

What other common 'minimal' vi's exist?

There is also xvi.sf.net mantained at github.com/martinwguy/xvi which is a different implementation based on STEVIE.

It's the smallest full-featured vi clone but has not been checked for POSIX compliant. Bug reports of variations from the standard would be welcome.