--help, however, may not be much good if you don't really understand the command in the first place. To get a bit more information, try the man (short for "manual") command:
man duThe man (manual) pages will give you more information about a command. It should cover what it is supposed to do, what options you can use, with details about how to use them, other relevant information, and suggestions of other related commands. Some manpages may also have a useful "examples" section. The start of the du manpage, shown in Figure 2, shows the standard format.
Man pages can be limited, and they're often not great if you're an absolute beginner, especially if the command is a complicated one. But they are often enough to get you started – and in some cases they can quite genuinely provide an entire manual. Check out man bash for a very comprehensive example.
One point to bear in mind is that there can be multiple categories of man page. The ones you are most likely to run across are:
1 Executable programs or shell commands 5 File formats and conventions eg /etc/passwd 8 System administration commands (usually only for root)(Type man man for further information.)
For an example of this, compare the output of man crontab with man 5 crontab. The first one describes the crontab command (this edits crontab files, which tell the program cron which tasks to run at what time). The second one describes the format that a crontab file should have. Both are obviously useful!
If you'd rather read manpages online, just type man command into Google.KDE's Konqueror Web and file browser has a built-in man page reader. Just type "man:[command name]", like "man:bash" in the URL bar. It even gives a list of alphabetical suggestions as you type--ed