GNU Info

(gawk.info)This Manual

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Using This Book
===============

     Documentation is like sex: when it is good, it is very, very good;
     and when it is bad, it is better than nothing.
     Dick Brandon

   The term `awk' refers to a particular program as well as to the
language you use to tell this program what to do.  When we need to be
careful, we call the program "the `awk' utility" and the language "the
`awk' language."  This Info file explains both the `awk' language and
how to run the `awk' utility.  The term "`awk' program" refers to a
program written by you in the `awk' programming language.

   Primarily, this Info file explains the features of `awk', as defined
in the POSIX standard.  It does so in the context of the `gawk'
implementation.  While doing so, it also attempts to describe important
differences between `gawk' and other `awk' implementations.(1) Finally,
any `gawk' features that are not in the POSIX standard for `awk' are
noted.

   There are subsections labelled as *Advanced Notes* scattered
throughout the Info file.  They add a more complete explanation of
points that are relevant, but not likely to be of interest on first
reading.  All appear in the index, under the heading "advanced notes."

   Most of the time, the examples use complete `awk' programs.  In some
of the more advanced sections, only the part of the `awk' program that
illustrates the concept currently being described is shown.

   While this Info file is aimed principally at people who have not been
exposed to `awk', there is a lot of information here that even the `awk'
expert should find useful.  In particular, the description of POSIX
`awk' and the example programs in *Note A Library of `awk' Functions:
Library Functions, and in Note: Practical `awk' Programs,
 should be of interest.

   Note: Getting Started with `awk', provides the
essentials you need to know to begin using `awk'.

   Note: Regular Expressions, introduces regular expressions in
general, and in particular the flavors supported by POSIX `awk' and
`gawk'.

   Note: Reading Input Files, describes how `awk' reads
your data.  It introduces the concepts of records and fields, as well
as the `getline' command.  I/O redirection is first described here.

   Note: Printing Output, describes how `awk' programs can
produce output with `print' and `printf'.

   Note: Expressions, describes expressions, which are the basic
building blocks for getting most things done in a program.

   Note: Patterns Actions and Variables,
describes how to write patterns for matching records, actions for doing
something when a record is matched, and the built-in variables `awk'
and `gawk' use.

   Note: Arrays in `awk', covers `awk''s one-and-only data
structure: associative arrays.  Deleting array elements and whole
arrays is also described, as well as sorting arrays in `gawk'.

   Note: Functions, describes the built-in functions `awk' and `gawk'
provide for you, as well as how to define your own functions.

   Note: Internationalization with `gawk',
describes special features in `gawk' for translating program messages
into different languages at runtime.

   Note: Advanced Features of `gawk', describes a
number of `gawk'-specific advanced features.  Of particular note are
the abilities to have two-way communications with another process,
perform TCP/IP networking, and profile your `awk' programs.

   Note: Running `awk' and `gawk', describes how to run
`gawk', the meaning of its command-line options, and how it finds `awk'
program source files.

   Note: A Library of `awk' Functions, and Note:
Practical `awk' Programs, provide many sample `awk'
programs.  Reading them allows you to see `awk' being used for solving
real problems.

   Note: The Evolution of the `awk' Language,
describes how the `awk' language has evolved since it was first
released to present.  It also describes how `gawk' has acquired
features over time.

   Note: Installing `gawk', describes how to get `gawk',
how to compile it under Unix, and how to compile and use it on different
non-Unix systems.  It also describes how to report bugs in `gawk' and
where to get three other freely available implementations of `awk'.

   Note: Implementation Notes, describes how to disable `gawk''s
extensions, as well as how to contribute new code to `gawk', how to
write extension libraries, and some possible future directions for
`gawk' development.

   Note: Basic Programming Concepts, provides some very
cursory background material for those who are completely unfamiliar
with computer programming.  Also centralized there is a discussion of
some of the issues involved in using floating-point numbers.

   The Note: Glossary, defines most, if not all, the significant
terms used throughout the book.  If you find terms that you aren't
familiar with, try looking them up.

   Note: GNU General Public License, and Note: GNU Free
Documentation License, present the licenses that cover the `gawk'
source code, and this Info file, respectively.

   ---------- Footnotes ----------

   (1) All such differences appear in the index under the heading
"differences between `gawk' and `awk'."