So you know that all the manual pages as grouped by sections based on what they do. So what do you do when
you want to list all commands at a given section? you tune the
apropos command as follows:
apropos --wildcard "*" --section <section_number>
One general knowledge question you can answer is this:
Find how many system calls are supported in linux, at the moment.
The manuals for all system calls are grouped in section 2. The answer becomes quite simple now.
$ apropos --wildcard "*" --section 2 | wc -l 471