Linux Application Documentation

From TWUUG

Many applications for Linux and Unix-like operating Systems come with a plethora of documentation installed on your computer when you install the application.

Many applications utilize the CLI Help function, the manual function and also place in-depth guides in the /usr/doc directory.

The CLI Help Function

Most application that can be run from the command line have a help function that displays some of the syntax information. Most application use the -h or --help flags to access this information., but in some cases the information is displayed if you enter an incomplete command. For an example lets see what the ping command will display. Type "ping --help" into your command line, the output is shown below.

user@linux:/$ ping --help
ping: invalid option -- -
Usage: ping [-LRUbdfnqrvVaA] [-c count] [-i interval] [-w deadline]
[-p pattern] [-s packetsize] [-t ttl] [-I interface or address]
[-M mtu discovery hint] [-S sndbuf]
[ -T timestamp option ] [ -Q tos ] [hop1 ...] destination

As you can see it did not accept the --help command, but it defaulted to the help page because the syntax was incorrect. Also the information is very brief and offers little explanation for the various functions.

For more descriptive information you will have to check another form of documentation.

Man or Manual Pages

Most applications come with a manual installed on your computer that you can access through the Command Line or your file browser.

Man Command Line Pages There are various ways to use man, the extent of which can be found by typing "man man" and accessing the man manual. The basic syntax is "man {section} {program}", the section can be omitted, but is useful in grabbing only the information you need from what can be a large manual.

For an example to ahead and type "man which" to access the manual for the which command. This displays quite a bit more information than the which help function. You navigate the manual files by using the arrows and page up/page down buttons, to exit the manual just hit q. If you scroll all of the way to the bottom of the document you will see the SEE ALSO portion where it shows bash(1), this means to refer to the first section of the bash man page which can be accessed by typing "man 1 bash".

Man HTML Files Some applications have HTML based manuals that you can access through your file browser by using the following syntax in the address bar, "man:{program} ".

The /usr/doc Directory

Many applications and daemon services are nice enough to include additional supplemental information in the /usr/doc directory within a folder by the application's name. The information they place their an include the license, README, Frequently Asked Questions, Bug lists and additional manual files. Feel free to explore the directory to get a better feel for the available information.