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Advanced Programming in the UNIX® Environment, Third Edition by Stephen A. Rago, W. Richard Stevens

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6. System Data Files and Information

6.1. Introduction

A UNIX system requires numerous data files for normal operation: the password file /etc/passwd and the group file /etc/group are two files that are frequently used by various programs. For example, the password file is used every time a user logs in to a UNIX system and every time someone executes an ls -l command.

Historically, these data files have been ASCII text files and were read with the standard I/O library. But for larger systems, a sequential scan through the password file becomes time consuming. We want to be able to store these data files in a format other than ASCII text, but still provide an interface for an application program that works with any file format. The portable ...

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