Where is the official documentation for chmod?

I would have expected it to be here in the gnu documentation but it is not.

So I Googled it and their were many links but I don’t know which one is the most “official”.

For example the first hit is for an Ubuntu distribution, and the second is for a Mac OS X distribution.

Answer

On a typical Linux system, the chmod command comes from the GNU coreutils package, and its canonical documentation is provided on their site.

Some Linux distributions can pick a different chmod (e.g. to fit on a small installation medium), in which case the documentation should be available via the man command or as part of the distribution’s documentation. Likewise, the documentation for Mac OS commands is available both as man pages and on Apple’s developer site.