Working Directly with System Calls

Previously, we learned that file descriptors are integers used by the operating system to represent open files and other resources. We now move from understanding descriptors to using them directly. In this lesson, we explore the core system calls and learn how to check return values, handle errors properly, and perform unbuffered I/O for precise control over data transfer.

Opening a file with open()

The open() system call is declared in <fcntl.h> and is used to request access to a file from the operating system. Below is the basic syntax: