Both diction and style are components in the same GNU package, and that’s a little surprising since they obviously do quite different things.
I fed style the same passage as I did diction, but rather than pluck out problematic words or phrases, style gives a technical and statistical analysis of the text. So no specific grammatical warnings, aside from a tally of how many conjunctions I used — oops, I mean, the writer used. 🙄
However, unless you’re familiar with those tests, the scores listed there are unlikely to mean anything to you. I’ll give you this as a starting link, and from there you can explore on your own. Each test has its own metric, and it may be that just word structure or even number of syllables can swing results in one direction or another.
Actual computation aside, style works in a very fast, very clean manner and presents its results in a useful table. Options-wise, style has flags for specific grammatical structures or voices, plus some triggers for sentence length or certain test results. If you want to screen out sentences more than 20 words long, for example, style is your tool.
So again, style is not so much a grammar checker as it is a writing analyzer, with the added ability to pop out lines that meet certain criteria. Kind of a like a grammar-grep, I guess.
I can’t necessarily endorse either diction or style as must-have tools if you do a lot of writing at the console, or even if you just do a lot of writing. They’re helpful, but might seem primitive compared with some conventional, contemporary applications. Keep them in mind though.
In the mean time, send me a link when you finish your text-based user interface grammar checker utility. The world awaits the arrival of your genius. 😉