This command sends a message with information regarding your current local (client) username and whether or not you are in admin mode. Note that your local username isn't the same as your server username.
The syntax for the whoami command is as follows:
Search our database of 61 Starbound commands...Onwards
Find below working examples of the whoami command.
After executing the above command, your local (client) username and administrator status will be printed to the chat.