Published on

Special Variables in Shell

variabledescription
$0The filename of the current script.
$nThese variables correspond to the arguments with which a script was invoked. Here n is a positive decimal number corresponding to the position of an argument (the first argument is 1,thesecondargumentis1, the second argument is 2, and so on).
$#The number of arguments supplied to a script.
$*All the arguments are double quoted. If a script receives two arguments, $\* is equivalent to $1 $2.
$@All the arguments are individually double quoted. If a script receives two arguments, @isequivalentto@ is equivalent to 1 $2.
$?The exit status of the last command executed.
$$The process number of the current shell. For shell scripts, this is the process ID under which they are executing.
$!The process number of the last background command.

Reference