apropos(1) just seaches a large text file called whatis. Each line in whatis contains the name, section number and short descrition of one man page in your installation. whatis is created by a script called /usr/sbin/makewhatis1?.
If you find that apropos(1) never finds anything there may be be no whatis file yet. Run /usr/sbin/makewhatis as root (see su(1)) and it will be created. (Note: /usr/sbin/makewhatis can sometimes take several minutes to finish.)
Section (3) man pages contain descriptions of C and TCL library functions for programmers. There are so many of these that they overwhelm everything else. You can remove them from whatis. As root, edit the script /usr/sbin/makewhatis. Around line 75 you will see a line like this,
Remove the "3". Run /usr/sbin/makewhatis again, and the section (3) entries will be gone.
alias apropos='apropos | grep -v "(3)"' does the same job, and is a little easier to undo when you happen to be programming and want those entries back.. --zcat(1)
All the time! Whenever I'm programming in C or C++ (or occasionally Python and Perl, if calling libc functions from there). What better way to refresh your memory of the correct order of arguments for memset(3), or to find out which header files you need to #include if you want to call the inet_addr(3) function? Sure beats getting out of the chair and finding a reference book :) --JohnMcPherson
Er, I'd be lost without man 2,3,4, 7 and 8! Hence why I'm constantly touching up their wiki pages (as I'm starting to try and use the wiki instead of man for these) -- Isomer