Set variables versus env variables Linux(debian) Bash shell

Question

When creating set variables, what is the advantage of adding them to environment? Both are lost at session termination. I know obviously I can add useful stuff to .bashrc that I would want to access via my user. Just not sure what the advantages would be? how common practice is it? do I need to worry about it? I am talking real life administration uses.

It seems to me like set is a local variable within a class. ENV is obviously global. Maybe the only use is when traversing different shells? How practical is it?

Answer 1

Environment variables are inherited by any process invoked by your shell. That includes both sub-shells and any other commands you invoke.

(Non-environment) shell variables are not.

For example, $TERM needs to be exported, because commands you invoke from your shell (a text editor, a pager, anything that uses a full-screen text display) needs to know what kind of terminal you're using, so it can look up its capabilities in termcap or terminfo. $LANG and similar variables need to be exported so that commands know about the current locale. $PATH needs to be exported so that any commands you invoke can then invoke other commands.

$PS1 , the shell prompt, does not need to be exported, because it's relevant only to the current shell (and is typically initialized for new shells).