Error handling and errno

Most of the system call functions in Linux and other UNIX-like systems set a special variable called errno when an error occurs. This way, we get a general error code from the return value (often -1) and then more specific information about what went wrong by looking at the errno variable.

In this recipe, we'll learn what errno is, how to read values from it, and when it is set. We'll also see an example use case of errno. Learning about errno is imperative to system programming, primarily since it's used in conjunction with system calls.

The next few recipes in this chapter are closely tied to this recipe. In this recipe, we'll learn about errno; in the following three recipes, we'll learn how to interpret the error codes we get from errno and print human-readable error messages.

Getting ready

You'll need the same components for this recipe that we used in the previous one; that is, the GCC compiler, the Make tool...