Positional parameters in the Bourne shell

When you run a shell procedure, the shell implicitly creates positional parameters that reference each word on the command line by its position on the command line.

The word in position 0 (the procedure name) is called $0, the next word (the first parameter) is called $1, and so on, up to $9. To refer to command line parameters numbered higher than 9, use the built-in shift command.

You can reset the values of the positional parameters explicitly by using the built-in set command.