Special Variables

Special variables in POSIX shell is specific to the type of shell program being used. Hence, there is no one "rule" that rules them all. You will need to refer to the shell program's specifications.

However, generally, they should not defer from one another. Here is the list I had for POSIX Bash and Dash. Please open it in a new tab or windows.

Once you're done, you may move on to the next sub-topic.