Mac OS X - Change ComputerName/HostName/LocalHostName via the command line

ComputerName - Used for Computer Name, File Sharing, and AppleTalk.

scutil --set ComputerName "YourComputerName"

HostName - Displayed in the default terminal command prompt.(user@hostname).

scutil --set HostName "YourHostName"

LocalHostName - Used for Bonjour-aware services on the local network.

scutil --set LocalHostName "YourLocalHostName"