The CLI has a built-in syntax helper. If you are unsure of the complete syntax for a particular command, enter as much of the command as possible, and then press [Tab] or ?. The syntax helper provides a list of options for the command, and places the cursor at the end of that portion of the command you already entered.
If you enter an invalid command, the syntax helper notifies you of your error, and indicates where the error is located.
If the command is one where the next option is a named component (such as a VLAN, access profile, or route map), the syntax helper also lists any currently configured names that might be used as the next option. In situations where this list is very long, the syntax helper lists only one line of names, followed by an ellipsis (...) to indicate that there are more names that can be displayed.
The syntax helper also provides assistance if you have entered an incorrect command.