how to set you distro to be a POSIX compliant?

You would need to be MUCH more specific with this question, or re-word the question to address one specific area or component of an operating system.

There is no single "setting" or "button" to set or click, to turn on or off POSIX compliance. Some OS's are more POSIX compliant than others though.

For starters, please open google.com and enter "Linux POSIX compliance". Examine some of the first 9 results you get, and you should then have a much better idea what exactly you're trying to ask.

Best regards!

not sure too but i'm trying to learn bash scripting and the ebook explains about something like a command "sa" for braise expansion and it returns command not found.

but maybe if this is a POSIX compliant, it might work.

I don't see how this `sa` command has anything to do with POSIX. Have a look at the manpage for `sa` to be sure.

It appears that you're trying to create an array of three elements in your last post, but I can't be sure if that was your intent. For what it's worth, 100% POSIX-compliant shells do not allow arrays. And, in Bash (a "POSIX-compliant" shell) you can use arrays, even if you start Bash with the --posix option.

Moral:

Code written in bash will not necessarily run in a 100% POSIX shell, unless the coder has been very careful to use only POSIX compliant code. Bash has a number of features that are "extra", and are available only in bash, and do not work in other shells.
On the other hand, code written in a 100% POSIX shell, will run in Bash.

You write:
So, I advise you re-read the ebook carefully and examine exactly what it says, because "about something like" is not concise enough that we can be sure we're on the same page here.

Cheers!