sleep: not consistent with the POSIX standard

[mssun]

I found that sleep is not consistent with the POSIX standard (http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sleep.html). It's more like a GNU implementation.

[Arcterus]

I don’t really believe this is an issue (because I think the extension is useful). Technically, all of the utilities don’t follow POSIX to the letter as they have --help and --version, which aren’t specified.

Currently the division between the utilities in the gnu feature and the posix feature are that the gnu utilities are not even specified in POSIX and are just additional utilities available in GNU projects.

[mssun]

Ok, thank for the explanation. I would be good to write down our standard to implement functions. E.g., what kinds of functions are worth to extend besides POSIX. If tools not mentioned in POSIX, what is our philosophy to implement them. I guess this will help potential contributors to have a clear understanding of our goal. Otherwise, they may get confused.

[Arcterus]

That sounds like a good idea. We might want to revise how the utilities are split up as well.