1.13 Getting Online Help

1.13 Getting Online Help

Linux systems come with a wealth of documentation. For basic commands, the manual pages (or man pages) tell you what you need to know. To access this manual, use the man command. For example, to see the manual page for the ls command, run man as follows:

man ls

Most manual pages concentrate primarily on reference information. They may contain some examples and cross-references, but that's about it. Don't expect a tutorial, and don't expect an engaging literary style. For programs with many options, the manual page often lists the options in some systematic way (for example, alphabetical order). It won't bother to tell you what the important ones are. If you are patient, you can usually find what you need to know. If you're excessively impatient, ask a friend, or pay someone to be your friend so that you can ask them.

To search for a manual page by keyword, use the -k option:

man -k keyword

This is helpful if you don't quite know the name of the command that you want.


If you have any additional questions about any of the commands described in the previous sections, you can find the answers with the man command.

Manual pages fall into numbered sections. When someone refers to a manual page, the section number appears in parentheses next to the name — ping(8), for example. Table 1-3 explains the section numbers:

Table 1-3: Online Manual Sections




User commands


Low-level system calls


Higher-level Unix programming library documentation


Device interface and driver information


File descriptions (system configuration files)




File formats, conventions, and encodings (ASCII, suffixes, and so on)


System commands and servers

Sections 1, 5, 7, and 8 are good supplements to this book. Section 4 may be of marginal use. Section 6 would be great if only it were a little larger.

You can select a manual page by section. This is sometimes important because man displays the first manual page that it finds for a particular search term. For example, if you want to see the /etc/passwd file description (as opposed to the passwd command), you can insert the section number before the page name:

man 5 passwd

Manual pages cover the essentials, but there are many more ways to get online help. If you're just looking for a certain option for a command, try typing a command name followed by --help or -h (the exact option varies from command to command). You may get a deluge (as in the case of ls --help), but you may find just what you're looking for.

Some time ago, the GNU Project decided that it didn't like manual pages very much and switched to another format called info (or texinfo). Often, this documentation goes further than a typical manual page, but it is sometimes more complex. To access an info page, use info with the command name:

info command

Some packages dump their available documentation into /usr/share/doc with no regard for online manual systems such as man or info. Have a look in this directory on your system if you find yourself searching for documentation. And as ever, don't hesitate to look for help on the Internet if you have a connection.