I need some help with C programming in Linux

Hello, I am using some functions that on error se some value to the errno variable, but I don't know how I can get the value of this variable. thanks.-

>>23

Translation: "John Carmack, the Nethack programmers, and anyone who ever wanted to write something as simple as string concatenation or making complex number arithmetic not-a-coding-eyesore have failed at life."

Which also translates to "I have no fucking idea what I'm talking about because I critique code more than I have ever written any of it."

>>23
people who replace global variables with things like passing extra arguments to every function, or some object that contains config settings, etc. and then act like this method is superior have not only failed at life but have shit all over it.