Now that you have tasted Linux it is time to introduce online Linux documentation facilities. You already know about man, because I told you to look things up in it. Maybe you even had read man documentation page. So anyway, what do you need to know about man to use it effectively?

To begin with, man pages are just compressed text files containing special markup so man program will know how to format them for you. In Debian they are located in /usr/share/man/. You can browse them by using zless. It is not even a program but a shell script, which uncompresses files and invokes less.

Next, I will quote man page about its sections:

1. Executable programs or shell commands
2. System calls (functions provided by the kernel)
3. Library calls (functions within program libraries)
4. Special files (usually found in /dev)
5. File formats and conventions eg /etc/passwd
6. Games
7. Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7)
8. System administration commands (usually only for root)
9. Kernel routines [Non standard]

It is exactly what it says on the tin. To invoke appropriate man section just type its section number, like: man 1. No worries if you do not understand what some section means, for now you will need only sections 1 and 8, which are about programs and system administrator utilities installed on your system. Additionally, you man already know what man(7) is for.

This are standard sections of a man page:

1. NAME — program name and short description.
2. SYNOPSIS — short list of available program options
3. DESCRIPTION — description of a program and explanation of available parameters.
4. OPTIONS — some man pages keep explanation of available parameters here.
5. EXIT STATUS — every program returns a code which indicates its success or failure. This code values are explained here.
6. RETURN VALUE — usually the same as EXIT STATUS.
7. ERRORS — known errors in a program.
8. ENVIRONMENT — environment variables. Set those before invoking the program.
9. FILES — usually, program configuration files.
10. VERSIONS — information about changes in program.
11. CONFORMING TO — notes about compatibility.
12. NOTES — information which an author of a man page did not know where to put.
13. BUGS — known errors in a program.
14. EXAMPLE — contains examples of program invocation. Very useful!
15. AUTHORS — who wrote the program.
16. SEE ALSO — related man pages.

Now about conventions, quoting again:

1. bold text — type exactly as shown.
2. italic text — replace with appropriate argument. This text mostly is displayed not italic, but like underlined.
3. [-abc] — any or all arguments within [ ] are optional.
4. -a|-b — options delimited by | cannot be used together.
5. argument … — argument is repeatable.
6. [expression] … — entire expression within [ ] is repeatable.

I will illustrate this by example. man less shows this:

Well, looks kinda scary I must say. First 4 lines are easy, just type what is shown and that is it:
1. less -?
2. less –help
3. less -V
4. less –version

Starting from line 5, as we can see, italic text is indeed shown as underlined. And, it looks totally incomprehensible. Let us go through it line by line.

5. less [-[+]aBcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~] — this looks more scary.

• First, it is optional because all arguments are enclosed in [].
• Second, when specifying an argument it must start with -. This is non-optional.
• Third, after - you may specify optional modifier +, which meaning is explained further in the manual.
• Fourth, you can specify one or several of commands which are shown as sequence of letters here. For example, you may type less -S .bashrc, or less -+S .bashrc, or less -SG .bashrc .profile or less -+SG .bashrc .profile

6. [-b space] [-h lines] [-j line] [-k keyfile] — simple enough, you may specify any of the keys shown -b, -h, -j, -k with parameters space, lines, line and keyfile respectively, which are explained in further in the manual.

7. [-{oO} logfile] [-p pattern] [-P prompt] [-t tag] — almost the same as line 6. -{oO} means that you may specify -o or -O, but not both at the same time.

8. [-T tagsfile] [-x tab,…] [-y lines] [-[z] lines] — again, almost the same as line 6. -x tab,… means that you may specify several values after -x, for example -x9 or -x9,17. -[z] lines means, that -z is optional, and you may just type less -10 instead of less -z10.

9. [-# shift] [+[+]cmd] [- -] [filename]… — this is somewhat more cryptic. +[+]cmd means that you may type less +cmd or less ++ cmd. - - is just a prefix. [filename]… reads one-or-more and means that you may specify several files when invoking less, for example less .bashrc, less .bashrc .profile, etc.

We are done! Not so scary, is it? Remember, because you are viewing manuals with less, to search what some key means type /key<ENTER> or &key<ENTER>. For example, to search what -T key means, type /-T<ENTER>.

Now I will give you list of useful man commands:

1. man -k . — list all man pages in your system. Not exactly very useful, but you may want to mediate on this list sometime. Or you can just count them all by typing man -k . | wc.
2. man -k [search string] — search something in man pages descriptions. Tye this: man -k tty.
3. man -wK [search string] - search something in man page bodies. Try man -wK tty.

Well, that is it for man. Now, there is another useful documentation utility, info. The command list is as follows:

1. info […] — invoke info. If you invoke it without arguments, it will take you to the index page.
2. <UP>, <DOWN>, <LEFT>, <RIGHT> allows you to scroll text.
3. <ENTER> open the link under cursor. Links start with * .
4. <TAB> — jump to the next link in document.
5. u — go up one level.
6. p — go to previous page, just like in browser.
7. n — go to next pages.
8. q — close info.

To start info with already familiar to you as I hope, vi keys, type info –vi-keys. Now you can scroll with j and k.

1. Type man man and try to decode SYNOPSIS section, which explains how it may be invoked.
2. Type info and h, read info help section.