Man
man title - manual page for specific command
man -k keyword prints list of pages that have this keyword
to add additional man pages you may need to rebuild file with mandb (Ubuntu, Suse)
makewhatis (Red Hat)
catman -w (Solaris, HP, AIX)
To check use: manpath
Input for man is located in usr/share/man directory
Linux compress it with gzip to save space, man will know how to uncompress them.
If necessery can be changed by setting MANPATH environment variable to override default path:
export MANPATH=
Sections of the man pages 1) user-level commands and applications 2) system calls and kernel errors 3) library calls 4) device drivers and network protocols 5) standart file format 6) games and demonstrations 7) miscellaneous files and documents 8) system administration commands 9) obscure kernel specs and interfaces