Mac OS X includes hundreds of commands derived from BSD UNIX that you can use with Terminal. To learn how to use a command, see the command’s “man” (manual) page. The man pages are typically written by programmers for use by other programmers and system administrators, but with careful reading you’ll learn about the capabilities of each command.
Open Terminal, and enter “man” and the name of the command.
For example, to learn about the uptime command, enter “man uptime” in the Terminal window.
Press the Space bar to display the next page, or type Q to quit.
For information about using man to display manual pages, enter “man man.” For information about viewing text in Terminal, enter “man more.”