# 6 Command Manuals It is a good habit to understand commands by looking into their manual page, e.g. find out the usage and options available for listing a directory, $ `man pow`.

The `include` tell us the header file needed when compiling The `Link with -lm`tell us we need "-lm" when compiling program with math functions Well, what does the number 3 mean in `POW(3)`? Man pages are divided into sections. The number corresponds to what section of the manual that page is from; 1 is Executable programs or shell commands, while 3 is Library calls. The man page for man itself (`man man`) explains it and lists the standard ones:

There are certain terms that have different pages in different sections (e.g.`printf`as a command appears in section 1, as a library call appears in section 3); in cases like that you can pass the section number to`man`before the page name to choose which one you want, or use`man -a`to show every matching page in a row: ``` $ man 1 printf $ man 3 printf $ man -a printf ```