(11-09-2016, 08:29 AM)pranomostro Wrote: Never implement a feature twice is exactly what having one single command for it is about.

But yet there are many different tools that can more or less do the same thing. For example of including a file in another, you can use cat(1) to concatenate one on top of the other. You can use m4(1) (general text preprocessor) or cpp(1) (C preprocessor) with include() or #include to target where to put it in. Want to include a file in a document? troff(1) has the .so request to source another file in.

Addendum: ESR has a koan on this matter.

(11-09-2016, 02:18 AM)venam Wrote: Most BSDs and Linux don't adhere to them, only the proprietary Unices do.

The difference between a certified POSIX system and a POSIX-compliant system is the fancy certificate.

(11-09-2016, 08:29 AM)pranomostro Wrote: Also, I am not sure how to think about huge software projects split into lots of small utilities. The git project comes into my mind. It is very complex, very complicated, very flexible and very fast. But is it truly unixy? I fear not.

Some projects are just complex by nature. Adhering to the Unix way isn't a strict codex but more as guidelines. If you have to break those guidelines, make sure there's some justification. What is more important is that the Git project has a goal. It does version control and considering its rise (GitHub partially to blame), it does it pretty well.