Inside Linux File Descriptors - Mastering the Basics

In this video, we take a deep dive into Linux file descriptors and how processes manage their open files. We'll break down the structures involved, from file descriptor tables to the kernel-wide file table and how they interact. This tutorial is designed to clarify how Linux keeps track of open files per process, what happens during file operations, and how multiple processes can share access to the same file. You'll learn: How file descriptors serve as unique identifiers for open files within a process. The role of the file descriptor table in each process. How the kernel's file table holds metadata and file state accessible across processes. What happens to file descriptors when a process forks. The differences between file-sharing scenarios and independent file operations. Key system calls like open(), read(), and write(). Timestamps: 0:00 – Intro: File Descriptor Table Overview 0:38 – Opening Files: Understanding int fd = open("file") 1:19 – Basics of the File Descriptor Table in Each Process 1:36 – How File Descriptors Map to the Kernel's File Table 2:10 – Process Forking and File Descriptor Inheritance 2:33 – Demonstration: File Offset Sharing between Parent and Child Processes 3:07 – Independent File Operations in Separate Processes 3:52 – File Descriptors explained 4:22 – Default File Descriptors (0, 1, 2) for Standard Streams 6:39 – Inode Table 7: 22 – Demonstration: Reading from Standard Input (read(0)) 8:15 – Writing to Files and the File Descriptor Table in Action