The Art of Unix Programming

The Art of Unix Programming

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The Art of Unix Programming

Eric Steven Raymond

Thyrsus Enterprises

<esr@thyrsus.com>

Copyright © 2003 Eric S. Raymond

Revision History

production.

Revision 0.3 22 January 2003 esr

First eighteen-chapter draft. Manuscript walkthrough at Chapter 12. Limited release for

early reviewers.

Revision 0.4 5 February 2003 esr

Release for public review.

Revision 0.41 11 February 2003 esr

Corrections and additions to Mac OS case study. A bit more about binary files as caches.

Added cite of Butler Lampson. Additions to history chapter. Note in futures chapter about

C and exceptions. Many typo fixes.

Preface

Who Should Read This Book

How To Use This Book

Related References

Conventions Used In This Book

Our Case Studies

Author's Acknowledgements

I. Context

1. Philosophy

Culture? What culture?

The Internet

The open-source community

Flexibility in depth

Unix is fun to hack

The lessons of Unix can be applied elsewhere

Basics of the Unix philosophy

Rule of Modularity: Write simple parts connected by clean interfaces.

Rule of Composition: Design programs to be connected with other

programs.

Rule of Clarity: Clarity is better than cleverness.

Rule of Least Surprise: In interface design, always do the least

surprising thing.

Rule of Repair: Repair what you can — but when you must fail, fail

noisily and as soon as possible.

Rule of Economy: Programmer time is expensive; conserve it in

preference to machine time.

Rule of Generation: Avoid hand-hacking; write programs to write

programs when you can.

Rule of Representation: Use smart data so program logic can be stupid

and robust.

sooner than you think.

The Unix philosophy in one lesson

Applying the Unix philosophy

Attitude matters too

2. History

Origins and history of Unix, 1969-1995

Genesis: 1969-1971

Exodus: 1971-1980

TCP/IP and the Unix Wars: 1980-1990

Blows against the empire: 1991-1995

Internet fusion and the Free Software Movement: 1981-1991

Cooperating processes

Internal boundaries

File attributes and record structures

Binary file formats

Preferred UI style

Who is the intended audience?

What are the entry barriers to development?

Operating-system comparisons

VMS

Mac OS

4. Modularity

Encapsulation and optimal module size

Compactness and orthogonality

Compactness

Orthogonality

The DRY rule

The value of detachment

Top-down, bottom-up, and glue layers

Case study: C considered as thin glue

Library layering

Coding for modularity

/etc/passwd style

RFC-822 format

Fortune-cookie format

XML

Windows INI format

Unix textual file format conventions

Application protocol design

Case study: SMTP, a simple socket protocol

Case study: POP3, the Post Office Protocol

Case study: IMAP, the Internet Message Access Protocol

6. Multiprogramming

Separating complexity control from performance tuning

Handing off tasks to specialist programs

Case study: the mutt mail user agent.

Pipes, redirection, and filters

Case study: Piping to a Pager

Case study: making word lists

Case study: pic2graph

Case study: bc(1) and dc(1)

Slave processes