“Part of the neatness of Unix is that you can just about do
everything programmatically in the same way that you do it by
hand. For example, you ever wonder why chmod() is called such?
Well, in writing my admintool program, I found out that if I wanted
to change the mode of a directory or ownership programmatically I
would just call a function named chmod(). So I started to explore
other aspects of the system calls and came across some really
useful ones.”
“Well, the first problem I ran into when programming with these
Unix system calls, was that after I started using the shadow
password database, it would coredump. I figured out that it was
because I was running the program as a normal user. I had to figure
out some way of identifying the current user running the program.
Here is where getuid() and geteuid() came in handy.”