[alphapapa]

Always use double-brackets [[ ]] if you're writing Bash (not sh) scripts. They are better.

Double-parentheses (( )) are only for arithmetic, e.g. "((count++))" or "echo $((1+1))"

The dollar sign precedes parentheses--i.e. $()--when you're substituting the output of a command, e.g. "echo Today is $(date)". It's easy to remember, because it's just like using the dollar sign for substituting the value of a variable, i.e. "date=$(date); echo $date".

You might want to look into the fish shell. Its scripting is much less idiosyncratic. You don't have to quote any variables, arrays, or command substitutions. e.g.:

    set foods apple banana 'cucumber casserole'
    for f in $foods
        echo $f
    end

prints:

    apple
    banana
    cucumber casserole

...not:

    apple
    banana
    cucumber
    casserole

...as would be the case if you forgot to quote "$foods" and "$f" in Bash.