Special Parameters

Parameter	Represents
$* $@	the value of all positional parameters combined
$#	the number of positional parameters
$0	the path to the current running script
$$	the process ID (PID) of the current process
$?	the exit code of the last executed command
$_	the last argument to the last executed command
$!	the process ID (PID) of the last command executed in the background
$_	the options flag currently in effect