BASH Special Vars

$1,$2,$3  //Positional params
"$@"      //Array of all positional params
"$*"      //IFS expansion of positional params
$#        //No. positional params
$-        //Shell options
$$        //PID of current shell
$         //Most recent param
$IFS      //Input field separator
$?        //Last exit status
$!        //PID of last command
$0        //Script name