In this book, I describe the programming interface of the Linux operating system: system calls, library functions, and other low-level interfaces that exist in Linux, a freely distributed implementation of UNIX. These interfaces are used directly or indirectly by every program running on Linux. They allow applications to perform the following operations:• file I/O;• creating and deleting files and directories;• creating new processes;• running programs;• setting timers;• communication between processes and threads on the same computer;• communication between processes running on different computers connected via a network.

This set of low-level interfaces is sometimes called the systems programming interface.

Although the main focus is on the Linux operating system, standards and issues are also discussed in detail related to portability. I make a clear distinction between Linux-specific topics and functionality that is typical of most UNIX implementations and is described in the POSIX standard as well as the Single UNIX Specification. In summary, this book offers a comprehensive treatment of the UNIX/POSIX API and can be used by programmers who write applications intended for other UNIX systems or create portable programs.