Hands-On System Programming with Go

Extensible commands

The current limitation of our pseudo-terminal is its extensibility. If a new command needs to be added, it needs to be added directly into the main package. We can think of a way of separating the commands from the main package and allowing other users to extend the functionality with their commands:

1. The first step is creating an exported command. Let's use an interface to define a command, so that the user can implement their own:

// Command represents a terminal commandtype Command interface {    GetName() string    GetHelp() string    Run(input io.Reader, output io.Writer, args ...string) (exit bool)}

2. Now we can specify a list of commands and a function for other packages to add other commands:

// ErrDuplicateCommand is ...