Robin Burk and David B. Horvath, CCP, et al
To Stephen P. Kowalchuk, who provided an IS manager and practicing network
administrator's point of view.
This edition is dedicated to my parents and grandparents. Education and doing
one's best was always important to them.
----David B. Horvath
Special thanks to Roger for support and grocery shopping. Also to the Laurelwood
English Cockers, who intuitively understand how to negotiate a communications session
(beg), allocate resources (if it's on the counter, it's ours!), and travel in encapsulated
cells (show crates) over broadband highway networks.
As with all the other projects I get involved with, my wife and muse, Mary, has
been tremendously supportive. Even when I spent my evenings and weekends at the keyboard.
Of course, she filled her time by shopping (she said this, not me).
My parents, brothers, and the rest of family, who always wondered about the time
I spent with computers, are now seeing the concrete results of it all.
I've been involved with this project for close to a year now. The development
staff were very helpful and have certainly kept it interesting. I want to thank them
and the other authors (especially those that I talked into helping out). This certainly
turned out to be a bigger project (and resulting book) than any of us expected. I
hope and expect that people will be looking at these two volumes as the definitive
After I take a short rest, I will be looking for the next project. Although these
things are really tiring, especially with the effort this one entailed, I miss them
when I'm not working on one.
---- David B. Horvath
About the Authors
Robin Burk has over 25 years' experience in advanced software, computer,
and data communications technologies. She has provided technical and managerial leadership
for the development of language tools, communications software, operating systems,
and multimedia applications. A successful executive in entrepreneurial companies,
she consults on software product development and the use of the Internet for business
success. Robin's undergraduate degree is in physics and math. She also holds an MBA
in finance and operations. Robin's other passion is breeding, training, and showing
dogs. She moderates an e-mail list for English Cocker Spaniel fanciers and can be
reached at email@example.com.
David B. Horvath, CCP, is a Senior Consultant with CGI Systems, Inc., an
IBM Company, in the Philadelphia, Pennsylvania area. He has been a consultant for
over twelve years and is also a part-time Adjunct Professor at local colleges teaching
topics that include C Programming, UNIX, and Database Techniques. He is currently
pursuing an M.S. degree in Dynamics of Organization at the University of Pennsylvania.
He has provided seminars and workshops to professional societies and corporations
on an international basis. David is the author of "UNIX for the Mainframer"
and numerous magazine articles.
When not at the keyboard, he can be found working in the garden or soaking in
the hot tub. He has been married for over ten years and has several dogs and cats.
David can be reached at firstname.lastname@example.org
for questions related to this book. No Spam please!
Chris Byers is a systems administrator for a financial securities firm
in Philadelphia. As a former consultant and disaster recovery specialist, he has
many years of experience in the UNIX world with its many different variants. He lives
in South Jersey with his wife, his son, and his cat. He can be reached at email@example.com.
With over two decades of full-time experience in information technology, Cameron
Laird now manages his own consultancy, Network Engineered Solutions, just outside
Houston. He has consistently found challenges during his career in bridging system
heterogeneities with high reliability, high precision, or high performance knowledge
bases. Most recently, that has meant engineering applications that combine components
written in a range of languages to solve needs in process control. His bias that
the most important communications requirements are those between humans has persistently
led him back to sidelines in writing. Hypertext <URL: http://starbase.neosoft.com/~claird/>
is his favorite medium.
Jeffrey A. Simon was graduated in 1970 from University of Minnesota Summa
cum Laude in Mathematics. He continued with graduate work in computer science at
the University of Minnesota, later obtaining his MBA from Pepperdine University.
For twenty-two years Mr. Simon has been professionally active in information systems
management and development. Over the last decade he has consulted for clients including
IBM, American Express, and CIGNA. He has conducted advanced information technology
training in the international environment, including seminars attended by representatives
of the U. S. Government, the U. S. Military, the Canadian Government, the British
Government, NATO, Boeing, Du Pont, Exxon, General Electric, Grand Metropolitan, Hewlett-Packard,
IBM, Monsanto, Siemens, Westinghouse, and numerous other major corporations. His
recent interests include the application of artificial intelligence to analysis of
the stock market.
David Till is a technical writer working in Toronto, Ontario, Canada. He
holds a master's degree in computer science from the University of Waterloo; programming
languages was his major field of study. He also has worked in compiler development
and on version-control software. He lists his hobbies as "writing, comedy, walking,
duplicate bridge, and fanatical support of the Toronto Blue Jays."
Sean Drew is a distributed object software developer, working primarily
with UNIX, C++, and CORBA. Sean is married to his college sweetheart Sheri and together
they have two children, Dylan Thomas and Terran Caitlin. At the time of this writing
a third child is on the way, and depending on the gender will probably be named Erin
Nichole, Brenna Nichole, or Ryan Patrick. When Sean is not busy with his family or
church, he likes to brew beer. Anybody up for a nice imperial stout? Sean can be
reached at firstname.lastname@example.org.
Matt Curtin is Chief Scientist at Megasoft Online, keeping busy in the
research and development of computer and network security, network computing, and
platform-independent application development. He is an active member of communities
related to firewalls, cryptography, and open operating systems. Previous to joining
Megasoft Online, he worked at AT&T Bell Laboratories in the design, implementation,
and management of firewalls, secure web servers, and Internet-based applications.
James Edwards (email@example.com)
is an IT professional experienced in data communications, network integration, and
systems design in both North America and Europe. He holds an M.S. in information
technology from the University of London and a B.A. (Hons) from Middlesex University,
both in the United Kingdom. James currently resides in Toronto, Canada, where he
is employed as a manager with the Deloitte & Touche Consulting Group. His spare
time is taken up with his girls, Denise, Lauren, and Poppy.
Michael R. Starkenburg is the Manager of Development and Operations for
Digital City Inc., where he leads a team of engineers creating online content delivery
systems and tools. Previously, he was responsible for the creation of the Internet's
largest web site, www.aol.com, and several other high profile web sites. He holds
degrees in business from The George Washington University and Saddleback College.
Mike can be reached at http://www.starkenburg.com
or mail to firstname.lastname@example.org.
Eric Goebelbecker has been working with market data and trading room systems
in the New York City area for the past six years. He is currently the Director for
Systems Development with MXNet Inc, a subsidiary of the Sherwood Group in Jersey
City, New Jersey, where he is responsible for developing new market data and transaction
Bill Ball, a retired U.S. Coast Guard photojournalist, has been playing
with and writing about computers since 1984.
Fred Trimble holds a master's degree in computer science from Villanova
University. In his nine years with Unisys Corporation, he held many positions, including
UNIX system administrator, C programmer, and Oracle database administrator. Currently,
he is a senior consultant and instructor with Actium Corporation in Conshohocken,
Pennsylvania, specializing in C++, Java, and the Brio data warehousing product line.
He is currently pursuing a master's degree in software engineering from Drexel University.
Jim Scarborough was an intern at Silicon Graphics for four years where
he worked with system administration, sales support, and technical support. He presently
works at a startup company in Huntsville, Alabama. For recreation, Jim enjoys amateur
radio (call sign KE4ROH) and ballroom dancing.
James C. Armstrong, Jr. is a software engineer with more than ten years
of industry experience with UNIX and C.
Tell Us What You Think!
As a reader, you are the most important critic and commentator of our books. We
value your opinion and want to know what we're doing right, what we could do better,
what areas you'd like to see us publish in, and any other words of wisdom you're
willing to pass our way. You can help us make strong books that meet your needs and
give you the computer guidance you require.
Do you have access to the World Wide Web? Then check out our site at http://www.mcp.com.
NOTE: If you have a technical question
about this book, call the technical support line at 317-581-3833 or send e-mail to
As the team leader of the group that created this book, I welcome your comments.
You can fax, e-mail, or write me directly to let me know what you did or didn't like
about this book--as well as what we can do to make our books stronger. Here's the
201 W. 103rd Street
Indianapolis, IN 46290
by Robin Burk and David B. Horvath, CCP
Welcome to the Second Edition of UNIX Unleashed.
Who Should Read This Book
Our highly popular first edition brought comprehensive, up-to-date information
on UNIX to a wide audience. That original edition was already 1,600 pages. The new
topics covered in this edition have obliged us to split the second edition into two
volumes, namely, the System Administrator's Edition and the Internet Edition,
which we'll refer to jointly as "the new" or the second edition. Though
each volume can stand alone and may be read independently of the other, they form
a complementary set with frequent cross-references. This new edition is written for:
- People new to UNIX
- Anyone using UNIX who wants to learn more about the system and its utilities
- Programmers looking for a tutorial and reference guide to C, C++, Perl, awk,
and the UNIX shells
- System administrators concerned about security and performance on their machines
- Webmasters and Internet server administrators
- Programmers who want to write Web pages and implement gateways to server databases
- Anyone who wants to bring his or her UNIX skills and knowledge base up-to-date
A lot has happened in the UNIX world since the first edition of UNIX Unleashed
was released in 1994. Perhaps the most important change is the tremendous growth
of the Internet and the World Wide Web. Much of the public Internet depends on UNIX-based
servers. In addition, many corporations of all sizes have turned to UNIX as the environment
for network and data servers. As UNIX fans have long known, the original open operating
system is ideal for connecting heterogeneous computers and networks into a seamless
What's New in UNIX Unleashed, Second Edition
This edition of UNIX Unleashed includes a substantial amount of new information
describing Internet and World Wide Web technologies in UNIX. New topics include:
- Programming Web pages with HTML
- Object-oriented programming in C++
- Programming Common Gateway Interfaces (CGI) using Perl, C/C++, HTML, and the
- MIME, the Multipurpose Internet Mail Extension
- HTTP, the HyperText Transfer Protocol
- Web servers and server performance
As UNIX becomes the platform of choice for critical network and data applications,
UNIX vendors have placed increased emphasis on system maturity, ease-of-use, and
security capabilities. Even with the growth of Microsoft Windows NT, UNIX still has
a place in the industry. It is more mature, more stable, more scaleable, and has
a wider array of applications than NT. Many people claim that NT is the open operating
system of the future; that may be true (I have my own personal opinion), but
for now, UNIX holds that place.
We've also updated this edition of UNIX Unleashed to bring you current
- Frequently Asked Questions (FAQs) about the most popular variants of UNIX
- Security issues and the technologies you can use to protect your system and its
information against intruders and malicious users
- The most popular Graphical User Interfaces (GUIs)
As with the original edition, we set out to bring users the most comprehensive,
useful, and up-to-date UNIX guide. To meet this goal, we've added nearly two dozen
new chapters and have revised much of the original material in the book. The resulting
book is so large that it is now divided into two volumes. The System Administrator's
Edition introduces UNIX and contains much of the information required for basic
users and for systems administrators. The Internet Edition includes advanced
information for programmers, Internet/Web developers, and those who need detailed
information regarding specific UNIX flavors.
Coverage of Popular UNIX Variants
Based on input from some of the experts, application developers, consultants,
and system administrators working in industry, we have provided information about
a number of the UNIX variants. We split the variants into two categories: major and
minor. This is not a comment on the quality or capabilities of the variant, but on
the penetration in the marketplace (popularity).
We consider AIX, HP-UX, Solaris, and SVR4 to be major and BSD, IRIX, Linux, and
SunOS to be minor players in the marketplace. There are other variants; the next
edition may cover them as they become more popular.
You can identify where something specific to a variant is discussed by the icon
next to it:
- AIX[em]major[em]IBM's version that runs on the RS/6000 series of RISC systems
and mainframes. Over 500,000 RS/6000 systems have been sold!
- BSD[em]minor[em]This version has a lesser presence in the marketplace. Although
many variants can trace their heritage to BSD, it is not that popular as a product.
- HP-UX[em]major[em]Hewlett Packard's (HP) version with a strong hardware presence
in the marketplace and a strong future growth path.
- IRIX[em]minor[em]While the Silicon Graphics (SGI) machines are wonderful for
graphics, they have not found wide acceptance in business environments.
- Linux[em]minor[em]Although this is a very nice and free variant, it has little
commercial presence in the marketplace (probably because corporations do not want
to run their mission-critical applications without a vendor they can sue when there
is a problem). See the SAMS Linux Unleashed series books (Red Hat and Slackware)
for detailed information.
- Solaris[em]major[em]Sun Microsystems' version with a strong hardware presence
in the marketplace and a strong future growth path.
- SunOs[em]minor[em]Largely being superseded by Solaris installations. A good variant,
but it is difficult for a company to support two versions of UNIX at a time.
- SVR4[em]major[em]This version has a strong presence in the marketplace. In addition,
many variants can trace their heritage to System V Release 4.
We've also enhanced our CD-ROM with a C compiler, the most popular Web server
software, and megabytes of other useful tools and information. The CD-ROM packaged
with each volume contains exactly the same software and materials. Here are some
of the noteworthy inclusions:
- The entire text of both volumes in HTML format
- Listings and code examples from various chapters in the volume
- FreeBSD 2.2.5, full binary release
- Linux Red Hat 4.2, full binary release [x86 platform only]
- BASH, sources and documentation.
- sendmail version 8.7
- RFCs 821, 822, 1425, 1123, 976, 977, 1036
- latest version of INN source code
- GNU findutils 4.1
- GNU fileutils 3.16
- disktool (v2.0)
- Crack (or equivalent)
- Perl 5.x
- elm and pine
- UNIX sort utility
- GNU awk, gawk
- APACHE web server
- GNU C compiler
- emacs editor
- NCSA Web Server
- Isearch and Isearch-cgi
- LessTif 0.80 sources, Linux and FreeBSD bins
- fvwm window manager
- Enlightenment window manager
- libg 2.7.2 (useful companion to C compiler)
- acroread, Adobe Acrobat PDF reader (for Linux and FreeBSD)
More information about the CD-ROM contents is available on the final page, "What's
on the CD-ROM."
To make use of the CD-ROM easier, whenever a reference in print is made to the
CD-ROM, you will see an icon. You can also scan through the text to find the CD-ROM
icons to find more information the disk contents.
How These Volumes are Organized
The books are divided into parts; detailed information about each volume is in
the next sections. Each volume also contains a glossary of terms and an index.
Whenever there is special information you should pay attention to, it will be
placed in a blocks to grab your attention. There are three types of special blocks:
note, tip, and caution.
NOTE: A note is used to provide you with information
that you may want to pay attention to but is not critical. It provides you with information
that can be critical but should not cause very much trouble.
TIP: A tip is used to make your life easier.
It provides you with information so you do not have to go digging for information
to solve a problem. These are based on real-life exposure to problems (and how they
CAUTION: A caution is used to grab your attention
to prevent you from doing something that would cause problems. Pay close attention
The icons shown in the CD-ROM Contents and Coverage of Popular UNIX Variants sections
also provide a quick means of referencing information.
How the System Administrator's Edition Is Organized
The first volume, UNIX Unleashed, Systems Administrator Edition, consists
of three major sections or parts. The general focus is getting you started using
UNIX, working with the shells, and then administering the system.
Part I, Introduction to UNIX, is designed to get you started using UNIX. It provides
you with the general information on the organization of the UNIX operating system,
how and where to find files, and the commands a general user would want to use. Information
is also provided on how to get around the network and communicating with other users
on the system.
Part II, UNIX Shells, provides you the information on how to choose which shell
to use and how to use that shell. The most popular shells: Bourne, Bourne Again (BASH),
Korn, and C, are covered as well as a comparison between them. Under UNIX, the shell
is what provides the user interface to the operating system.
Part III, System Administration, gets you started and keeps you going with the
tasks required to administer a UNIX system. From installation through performance
and tuning, the important topics are covered. The general duties of the system administrator
are described (so you can build a job description to give to your boss). In case
you are working on a brand-new UNIX system, the basics of UNIX installation are covered.
Other topics covered in this section include: starting and stopping UNIX, user administration,
file system and disk administration, configuring the kernel (core of the operating
system), networking UNIX systems, accounting for system usage, device (add-on hardware)
administration, mail administration, news (known as netnews or UseNet) administration,
UUCP (UNIX to UNIX Copy Program, an early networking method still in wide use today)
administration, FTP (File Transfer Protocol) administration, and finally, backing
up and restoring files.
How the Internet Edition Is Organized
The second volume, UNIX Unleashed, Internet Edition, consists of seven
major parts. The general focus is programming (GUI, application languages, and the
Internet), text formatting (which involves embedding commands in your text and then
processing it), security considerations (advanced system administration), developing
for the Internet, "programming," getting you started using UNIX, working
with the shells, and source code control and configuration management, and Frequently
Asked Questions (FAQ) for the different variants of UNIX.
Part I, Graphical User Interfaces, provides you with information about using and
writing GUI applications. When the operating system is UNIX, the GUI is the X-windowing
Part II, Programming, introduces the most popular program development tools in
the UNIX environment. The most important part is how to enter your program (editing
with vi and emacs)! The awk, Perl, C, and C++ programming languages are covered.
Awk and Perl are interpreted languages designed for quick program development. C
is the compiled language developed by Kernighan and Ritchie[em]UNIX is written in
this language. C++ is an enhancement to the C language that supports object oriented
programming. The final chapter in this section discusses the make utility,
which provides a rule-based method to control program compilation.
Part III, Text Formatting and Printing, covers the tools that support the development,
formatting, and printing of documents in the UNIX environment. These tools were much
of the original justification for hardware that was used to develop UNIX. The formatting
programs, nroff and troff, the standard macro packages, and many
of the other document preparation tools are covered. In addition, developing your
own text formatting macros is discussed.
Part IV, Security, is an advanced area of systems administration. One of the criticisms
of UNIX is that it is not secure. It was developed in an environment where the individuals
were trusted and sharing information was important. UNIX is capable of being very
secure; you just have to know how to set it up. This section provides that information.
The risks, available tools, and helpful organizations are covered.
Part V, UNIX and the Internet, introduces the tools used with the world wide web
and the transmission of binary files via email (MIME). The web page definition language,
HTML, is introduced, along with the methods of developing CGI (Common Gateway Interface[em]programs
that run on the web server processing data from web pages) programs in shell scripting
languages, Perl, and C/C++. Administrative information is provided in chapters on
HTTP (HyperText Transport Protocol) and monitoring server activity.
Part VI, Source Control, covers the tools that UNIX provides to maintain control
of your source code as different versions (and revisions) are created. The three
major tools are RCS, CVS, and SCCS.
Part VII, Frequently Asked Questions, provides answers, as the name implies, to
the most frequently asked questions about the various variants of UNIX. AIX, BSD,
HP-UX, Linux, Solaris, SVR4, and IRIX are covered in individual chapters.
Conventions Used in This Volume
This book uses the following typographical conventions:
- Menu names are separated from the individual menu options with a vertical bar
(|). For example, "File|Save" means "Select the File menu and then
choose the Save option."
- New terms appear in italic.
- All code appears in monospace. This includes pseudocode that is used
to show a general format rather than a specific example.
- Words that you are instructed to type appear in monospace bold.
- Placeholders (words that stand for what you actually type) appear in italic
- Lines of code that are too long to fit on only one line of this book are broken
at a convenient place and continued on the next line. A code continuation character
precedes the new line. Any code that contains this character should be entered as
one long line without a line break.
- An ellipsis (...) in code indicates that some code has been omitted for the sake