[turminal]

Pretty much everything is in conflict.

POSIX standarized and attempted to unify a dozen different incompatible systems that developed independently on top of the original unix from bell labs. Those systems were developed by building new functionality on top of what unix provided. In order to keep at least some sort of compatibility the old and at times obsolete functionality was kept in the system.

Plan 9 on the other hand intentionally broke compatibility with its predecessors and had those same features that were glued recklessly on top of each other in various unices thoughtfully redesigned from scratch, often omitting stuff that didn't seem relevant enough to its authors.

[pjmlp]

Additionally it also took the role of being C's standard library that ISO C did not want to take upon themselves.