Header Files

You can learn a lot about the system functions that are available and how to use them by looking at the system header files. These reside in /usr/include and /usr/include/sys. These header files make good reading for inquiring minds. Don't include them directly in your programs, though; always use the header files in /usr/include or as mentioned in the man page for the function you're using. The source code for the Linux kernel itself is usually stored under /usr/src/linux.