#TIL : Internal Variables in BASH

$PWD

Your current working directory, so you don't have to use CWD=$(pwd)

$OLDPWD

Your previous working directory

Note : You can jump directly to it by the command cd -

$SECONDS

The number of seconds the script has been running

You can use it for profiling or limiting timeout

TIME_LIMIT=60
START=$SECONDS
while [ $(($SECONDS - START)) -le "$TIME_LIMIT" ]
do
	## Your work here
done

echo "It takes $SECONDS seconds to get here !"

$RANDOM

Get random integer number, for getting random name or just roll a dice ;)