shell-parameter-expansion

Variable	Description
$$	This is the process ID of the script itself.
$0	The first parameter to the shell, which is typically the path of the shell itself. If this parameter starts with - then the shell is assumed to be a Login Shell.
$-	The flags that were set for the shell, such as i for 'interactive'.
$0	The first parameter to the shell, which is typically the path of the shell itself.
$1	The first parameter
$2	The second parameter
${11}	The 11th parameter - if the parameter is more than one digit you must surround it with braces
$#	The number of parameters
$@	The full set of parameters as an array
$*	The full set of parameters as a string separated by the first value in the $IFS variable
${@:start:count}	A subset of 'count' parameters starting at parameter number 'start'
$?	The status code of the most recently called command.

TODO

Need to update Chapter 19 to link to this.