RVAL to Return Strings from Shell FunctionsEven though the actual name RVAL is hard to remember and doesn’t
matter. (I’ve see RETURN and RSTRING used as well.) This convention
gets around the fact that Shell script functions cannot return anything
but an integer. You could just as well echo the value. Many do. But
that does, in fact, force a subshell to do that work. I believe Bash has
been optimized to do it so quickly you don’t even realize it. But
nevertheless, using RVAL is faster.
Note that this causes your shell scripts to not be asynchronous but you should never use concurrency within your shell scripts anyway. That’s just fucking stupid.