Shells and Scripting (12)

Some shell built-in variables with pre-assigned values:

`$0`		the name of the command
`$1`		the first command-line argument
`$2`		the second command-line argument
`$3`		the third command-line argument
`$#`		count of command-line arguments
`$*`		all of the command-line arguments (together)
`$@`		all of the command-line arguments (separately)
`$?`		exit status of the most recent command
`$$`		process ID of this shell

The last one is useful for generating unique filenames.