How to check whether an environment variable is read only or R+W?

Question

How to check whether an environment variable is read only or R+W on linux system?

As an example BASH_VERSINFO is readonly. do i need to check manual? Any other option?

Answer 1

The command that makes variables read-only is readonly, e.g. readonly FOO=bar.

If you call it without arguments, it prints all readonly variables. Check if yours is in there. For me, the following command reduces output to the variable names, one per line:

readonly | cut -d= -f1 | cut -d' ' -f3