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This Info file teaches you about the awk
language and
how you can use it effectively. You should already be familiar with basic
system commands, such as cat
and ls
,(1) and basic shell
facilities, such as Input/Output (I/O) redirection and pipes.
Implementations of the awk
language are available for many different
computing environments. This Info file, while describing the awk
language
in general, also describes a particular implementation of awk
called
gawk
(which stands for "GNU Awk"). gawk
runs on a broad range
of Unix systems, ranging from 80386 PC-based computers, up through large scale
systems, such as Crays. gawk
has also been ported to MS-DOS and
OS/2 PC's, Atari and Amiga micro-computers, and VMS.
History of awk
andgawk
The history of gawk
andawk
.The GNU Project and This Book Brief history of the GNU project and this Info file. Acknowledgements
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awk
and gawk
The name awk
comes from the initials of its designers: Alfred V.
Aho, Peter J. Weinberger, and Brian W. Kernighan. The original version of
awk
was written in 1977 at AT&T Bell Laboratories.
In 1985 a new version made the programming
language more powerful, introducing user-defined functions, multiple input
streams, and computed regular expressions.
This new version became generally available with Unix System V Release 3.1.
The version in System V Release 4 added some new features and also cleaned
up the behavior in some of the "dark corners" of the language.
The specification for awk
in the POSIX Command Language
and Utilities standard further clarified the language based on feedback
from both the gawk
designers, and the original Bell Labs awk
designers.
The GNU implementation, gawk
, was written in 1986 by Paul Rubin
and Jay Fenlason, with advice from Richard Stallman. John Woods
contributed parts of the code as well. In 1988 and 1989, David Trueman, with
help from Arnold Robbins, thoroughly reworked gawk
for compatibility
with the newer awk
. Current development focuses on bug fixes,
performance improvements, standards compliance, and occasionally, new features.
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The Free Software Foundation (FSF) is a non-profit organization dedicated to the production and distribution of freely distributable software. It was founded by Richard M. Stallman, the author of the original Emacs editor. GNU Emacs is the most widely used version of Emacs today.
The GNU project is an on-going effort on the part of the Free Software
Foundation to create a complete, freely distributable, POSIX compliant
computing environment. (GNU stands for "GNU's not Unix".)
The FSF uses the "GNU General Public License" (or GPL) to ensure that
source code for their software is always available to the end user. A
copy of the GPL is included for your reference
(see section GNU GENERAL PUBLIC LICENSE).
The GPL applies to the C language source code for gawk
.
A shell, an editor (Emacs), highly portable optimizing C, C++, and
Objective-C compilers, a symbolic debugger, and dozens of large and
small utilities (such as gawk
), have all been completed and are
freely available. As of this writing (early 1997), the GNU operating
system kernel (the HURD), has been released, but is still in an early
stage of development.
Until the GNU operating system is more fully developed, you should
consider using Linux, a freely distributable, Unix-like operating
system for 80386, DEC Alpha, Sun SPARC and other systems. There are
many books on Linux. One freely available one is Linux
Installation and Getting Started, by Matt Welsh.
Many Linux distributions are available, often in computer stores or
bundled on CD-ROM with books about Linux.
(There are three other freely available, Unix-like operating systems for
80386 and other systems, NetBSD, FreeBSD,and OpenBSD. All are based on the
4.4-Lite Berkeley Software Distribution, and they use recent versions
of gawk
for their versions of awk
.)
This Info file itself has gone through several previous,
preliminary editions. I started working on a preliminary draft of
The GAWK Manual, by Diane Close, Paul Rubin, and Richard
Stallman in the fall of 1988.
It was around 90 pages long, and barely described the original, "old"
version of awk
. After substantial revision, the first version of
the The GAWK Manual to be released was Edition 0.11 Beta in
October of 1989. The manual then underwent more substantial revision
for Edition 0.13 of December 1991.
David Trueman, Pat Rankin, and Michal Jaegermann contributed sections
of the manual for Edition 0.13.
That edition was published by the
FSF as a bound book early in 1992. Since then there have been several
minor revisions, notably Edition 0.14 of November 1992 that was published
by the FSF in January of 1993, and Edition 0.16 of August 1993.
Edition 1.0 of Effective AWK Programming represents a significant re-working of The GAWK Manual, with much additional material. The FSF and I agree that I am now the primary author. I also felt that it needed a more descriptive title.
Effective AWK Programming will undoubtedly continue to evolve.
An electronic version
comes with the gawk
distribution from the FSF.
If you find an error in this Info file, please report it!
See section Reporting Problems and Bugs, for information on submitting
problem reports electronically, or write to me in care of the FSF.
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I would like to acknowledge Richard M. Stallman, for his vision of a better world, and for his courage in founding the FSF and starting the GNU project.
The initial draft of The GAWK Manual had the following acknowledgements:
Many people need to be thanked for their assistance in producing this manual. Jay Fenlason contributed many ideas and sample programs. Richard Mlynarik and Robert Chassell gave helpful comments on drafts of this manual. The paper A Supplemental Document forawk
by John W. Pierce of the Chemistry Department at UC San Diego, pinpointed several issues relevant both toawk
implementation and to this manual, that would otherwise have escaped us.
The following people provided many helpful comments on Edition 0.13 of The GAWK Manual: Rick Adams, Michael Brennan, Rich Burridge, Diane Close, Christopher ("Topher") Eliot, Michael Lijewski, Pat Rankin, Miriam Robbins, and Michal Jaegermann.
The following people provided many helpful comments for Edition 1.0 of Effective AWK Programming: Karl Berry, Michael Brennan, Darrel Hankerson, Michal Jaegermann, Michael Lijewski, and Miriam Robbins. Pat Rankin, Michal Jaegermann, Darrel Hankerson and Scott Deifik updated their respective sections for Edition 1.0.
Robert J. Chassell provided much valuable advice on the use of Texinfo. He also deserves special thanks for convincing me not to title this Info file How To Gawk Politely. Karl Berry helped significantly with the TeX part of Texinfo.
David Trueman deserves special credit; he has done a yeoman job
of evolving gawk
so that it performs well, and without bugs.
Although he is no longer involved with gawk
,
working with him on this project was a significant pleasure.
Scott Deifik, Darrel Hankerson, Kai Uwe Rommel, Pat Rankin, and Michal
Jaegermann (in no particular order) are long time members of the
gawk
"crack portability team." Without their hard work and
help, gawk
would not be nearly the fine program it is today. It
has been and continues to be a pleasure working with this team of fine
people.
Jeffrey Friedl provided invaluable help in tracking down a number
of last minute problems with regular expressions in gawk
3.0.
David and I would like to thank Brian Kernighan of Bell Labs for
invaluable assistance during the testing and debugging of gawk
, and for
help in clarifying numerous points about the language. We could not have
done nearly as good a job on either gawk
or its documentation without
his help.
I would like to thank Marshall and Elaine Hartholz of Seattle, and Dr.
Bert and Rita Schreiber of Detroit for large amounts of quiet vacation
time in their homes, which allowed me to make significant progress on
this Info file and on gawk
itself. Phil Hughes of SSC
contributed in a very important way by loaning me his laptop Linux
system, not once, but twice, allowing me to do a lot of work while
away from home.
Finally, I must thank my wonderful wife, Miriam, for her patience through
the many versions of this project, for her proof-reading,
and for sharing me with the computer.
I would like to thank my parents for their love, and for the grace with
which they raised and educated me.
I also must acknowledge my gratitude to G-d, for the many opportunities
He has sent my way, as well as for the gifts He has given me with which to
take advantage of those opportunities.
Arnold Robbins
Atlanta, Georgia
February, 1997
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