Using on-line documentation
General
You have used to use Help-feature in Borland or Visual C environment. There is on-line help
available in Linux-environment too.
Sections of manual pages
Manuals of Unix-systems are divided into sections in the following way:
1. User commands
2. System Calls
3. Library functions
4. Special files (Devices)
5. (File formats and conversions
6. Games for Linux
7. (Macro packages and conventions
8. System Management Commands
9. Kernel routines
During the program development you need especially man pages from section 2 and 3.
How to open a manual page
You can open the man page of a certain command/system call/library function by entering its
name after the command man. Then the system searches the keyword (name of the
command/system calls/library function) from the sections of manuals in the order given
above. A small problem may arise for example if there is a user command and a system call
that both have the same name. An example of this kind of command is read, because it is a
user command as well as system call. If you enter a command
man read,
what you get, is the man page of user command read, but not of system call read, what you
may have expected when programming. The reason for this is, that manual sections are
searched in the order given above and it means that man commands opens the man page from
section 1, that is man page of user command read. If you in this case want a man page of
system call read you have to indicate explicitly the section number you want to be searched. In
this case it means that the command you should give would be
man 2 read
If you don’t even remember the name of command/system call/library function you can ask
man command to search using keyword. This is done using option –k followed by the search
key in man command in the following way:
man –k string
where we ask man to find man pages where keyword string is present. The result of that
command is a list where we can see what manual pages (and in what section) contain the
keyword.
How to move and search inside a manual page and quitting
When manual pages are displayed on the screen less-program is used automatically. It means
that you can move inside manual pages using the following keys:
Cursor keys DOWN and UP can be used to one line down or up.
f or ctrl-f scrolls one screenfull forward (space does the same thing)
b or ctrl-b scrolls one screenfull forward
q (quit) lets you out from manual page.
The man page of one topic is not very long usually. It may be useful sometimes to search a
keyword from inside the opened man page. This can be done by pressing / and entering the
search key. For example if you inside manual page enter /string it searches the keyword string
and highlights all found string words.
Hint.
When you are developing programs, it is useful to open a separate terminal for using
man pages. When the program development (editing, compiling, running) is done in
a separate window it is easy to switch to man page terminal to get help and back
again.
HOWTO-documents
The man pages discussed above describe the individual command/system call/library
functions. Unix-systems also offer so-called HOWTO-documents to the users and developers.
HOWTO-documents describe and explain wider things than individual commands. The basic
idea is that they describe ”how to do something”. There are several separate HOWTO-
documents in the system.
How to exploit X-environment and Internet browser
In the windowed environment (containing so called X), as is the case in our laboratory
(River), it is possible to keep the separate terminals mentioned above open simultaneously on
the desktop to make switching between man pages and program editing/compiling easy.
The windowed system has a separate graphical program to use man pages that is called xman.
In the windowed system (like in lab) you can use the web-browser as well. This means that all
resources in the Internet are available, for example Google.
A good starting point is Linux Documentation Project (LDP). The Internet address of that is
www.tldp.org
The man pages as well as HOWTO-documents are available in the web too.