handle link commands

def cmd_link(self, args):
        '''handle link commands'''
        if len(args) < 1:
            self.show_link()
        elif args[0] == "list":
            self.cmd_link_list()
        elif args[0] == "add":
            if len(args) != 2:
                print("Usage: link add LINK")
                return
            self.cmd_link_add(args[1:])
        elif args[0] == "ports":
            self.cmd_link_ports()
        elif args[0] == "remove":
            if len(args) != 2:
                print("Usage: link remove LINK")
                return
            self.cmd_link_remove(args[1:])
        else:
            print("usage: link <list|add|remove>")