There are many help resources available for Unix. Depending on your needs, you can approach your search for information in several ways. The following are some methods with which you are now familiar:
Unix Manual Pages— Use the man command to display full information about a specific command. The apropos, man -k, man -f, and whatis commands can display summary information and search for a specific type of command.
Built-in Help System— Many programs have built-in help that can be displayed with a command-line argument, usually --help or -h.
Documentation— Every installation of Unix ends up with a little something that reflects the personality of the system administrator, so every installation is a little different. Local documentation ...