Introduction

This book describes the programming interface to the Unix systemthe system call interface and many of the functions provided in the standard C library. It is intended for anyone writing programs that run under Unix.

Like most operating systems, Unix provides numerous services to the programs that are runningopen a file, read a file, start a new program, allocate a region of memory, get the current time-of-day, and so on. This has been termed the system call interface. Additionally, the standard C library provides numerous functions that are used by almost every C program (format a variable's value for output, compare two strings, etc.).

The system call interface and the library routines have traditionally been described in Sections 2 and 3 of the Unix Programmer's Manual. This book is not a duplication of these sections. Examples and rationale are missing from the Unix Programmer's Manual, and that's what this book provides.