2 - Raspberry PI Community Projects

Man pages not only document programs accessible from the command line, but also configuration
files, system calls, C library functions, and so forth. Sometimes names can collide. For
example, the shell's read command has the same name as the system call read. This is why
manual pages are organized in numbered sections:
1. commands that can be executed from the command line;
2. system calls (functions provided by the kernel);
3. library functions (provided by system libraries);
4. devices (under Unix, these are special files, usually placed in the /dev/ directory);
5. config files (formats and conventions);
6. games;
7. sets of macros and standards;
8. system administration commands;
9. kernel routines.
It is possible to specify the section of the manual page that you are looking for: to view the documentation
for the read system call, you would type man 2 read. When no section is explicitly
specified, the first section that has a manual page with the requested name will be shown. Thus,
man shadow returns shadow(5) because there are no manual pages for shadow in sections 1 to 4.
TIP
whatis
If you do not want to look at the full manual page, but only a short description
to confirm that it is what you are looking for, simply enter whatis command.
$ whatis scp
scp (1)
- secure copy (remote file copy program)
This short description is included in the NAME section at the beginning of all
manual pages.
Of course, if you do not know the names of the commands, the manual is not going to be of much
use to you. This is the purpose of the apropos command, which helps you conduct a search in
the manual pages, or more specifically in their short descriptions. Each manual page begins
essentially with a one line summary. apropos returns a list of manual pages that mention the
keyword(s) requested. If you choose them well, you will find the name of the command that
you need.
Chapter 7 — Solving Problems and Finding Relevant Information
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