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General Introduction
********************

This file documents `awk', a program that you can use to select
particular records in a file and perform operations upon them.

Copyright (C) 1989, 1991, 1992, 1993, 1996, 1997, 1998, 1999, 2000,
2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.


   This is Edition 3 of `GAWK: Effective AWK Programming: A User's
Guide for GNU Awk', for the 3.1.5 (or later) version of the GNU
implementation of AWK.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License", the Front-Cover
texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below).  A copy of the license is included in the section entitled
"GNU Free Documentation License".

  a. "A GNU Manual"

  b. "You have freedom to copy and modify this GNU Manual, like GNU
     software.  Copies published by the Free Software Foundation raise
     funds for GNU development."

Foreword: Some nice words about this
Preface: What this Info file is about; brief
Getting Started: A basic introduction to using
Regexp: All about matching things using regular
Reading Files: How to read files and manipulate fields.
Printing: How to print using `awk'. Describes
Expressions: Expressions are the basic building blocks
Patterns and Actions: Overviews of patterns and actions.
Arrays: The description and use of arrays. Also
Functions: Built-in and user-defined functions.
Internationalization: Getting `gawk' to speak your
Advanced Features: Stuff for advanced users, specific to
Invoking Gawk: How to run `gawk'.
Library Functions: A Library of `awk' Functions.
Sample Programs: Many `awk' programs with complete
Language History: The evolution of the `awk'
Installation: Installing `gawk' under various
Notes: Notes about `gawk' extensions and
Basic Concepts: A very quick intoduction to programming
Glossary: An explanation of some unfamiliar terms.
Copying: Your right to copy and distribute
GNU Free Documentation License: The license for this Info file.
Index: Concept and Variable Index.
History: The history of `gawk' and
Names: What name to use to find `awk'.
This Manual: Using this Info file. Includes
Conventions: Typographical Conventions.
Manual History: Brief history of the GNU project and this
How To Contribute: Helping to save the world.
Acknowledgments: Acknowledgments.
Running gawk: How to run `gawk' programs;
One-shot: Running a short throwaway `awk'
Read Terminal: Using no input files (input from terminal
Long: Putting permanent `awk' programs in
Executable Scripts: Making self-contained `awk'
Comments: Adding documentation to `gawk'
Quoting: More discussion of shell quoting issues.
Sample Data Files: Sample data files for use in the
Very Simple: A very simple example.
Two Rules: A less simple one-line example using two
More Complex: A more complex example.
Statements/Lines: Subdividing or combining statements into
Other Features: Other Features of `awk'.
When: When to use `gawk' and when to use
Regexp Usage: How to Use Regular Expressions.
Escape Sequences: How to write nonprinting characters.
Regexp Operators: Regular Expression Operators.
Character Lists: What can go between `[...]'.
GNU Regexp Operators: Operators specific to GNU software.
Case-sensitivity: How to do case-insensitive matching.
Leftmost Longest: How much text matches.
Computed Regexps: Using Dynamic Regexps.
Locales: How the locale affects things.
Records: Controlling how data is split into records.
Fields: An introduction to fields.
Nonconstant Fields: Nonconstant Field Numbers.
Changing Fields: Changing the Contents of a Field.
Field Separators: The field separator and how to change it.
Regexp Field Splitting: Using regexps as the field separator.
Single Character Fields: Making each character a separate field.
Command Line Field Separator: Setting `FS' from the command-line.
Field Splitting Summary: Some final points and a summary table.
Constant Size: Reading constant width data.
Multiple Line: Reading multi-line records.
Getline: Reading files under explicit program
Plain Getline: Using `getline' with no arguments.
Getline/Variable: Using `getline' into a variable.
Getline/File: Using `getline' from a file.
Getline/Variable/File: Using `getline' into a variable from a
Getline/Pipe: Using `getline' from a pipe.
Getline/Variable/Pipe: Using `getline' into a variable from a
Getline/Coprocess: Using `getline' from a coprocess.
Getline/Variable/Coprocess: Using `getline' into a variable from a
Getline Notes: Important things to know about
Getline Summary: Summary of `getline' Variants.
Print: The `print' statement.
Print Examples: Simple examples of `print' statements.
Output Separators: The output separators and how to change
OFMT: Controlling Numeric Output With
Printf: The `printf' statement.
Basic Printf: Syntax of the `printf' statement.
Control Letters: Format-control letters.
Format Modifiers: Format-specification modifiers.
Printf Examples: Several examples.
Redirection: How to redirect output to multiple files
Special Files: File name interpretation in `gawk'.
Special FD: Special files for I/O.
Special Process: Special files for process information.
Special Network: Special files for network communications.
Special Caveats: Things to watch out for.
Close Files And Pipes: Closing Input and Output Files and Pipes.
Constants: String, numeric and regexp constants.
Scalar Constants: Numeric and string constants.
Nondecimal-numbers: What are octal and hex numbers.
Regexp Constants: Regular Expression constants.
Using Constant Regexps: When and how to use a regexp constant.
Variables: Variables give names to values for later
Using Variables: Using variables in your programs.
Assignment Options: Setting variables on the command-line and a
Conversion: The conversion of strings to numbers and
Arithmetic Ops: Arithmetic operations (`+', `-',
Concatenation: Concatenating strings.
Assignment Ops: Changing the value of a variable or a
Increment Ops: Incrementing the numeric value of a
Truth Values: What is ``true'' and what is ``false''.
Typing and Comparison: How variables acquire types and how this
Boolean Ops: Combining comparison expressions using
Conditional Exp: Conditional expressions select between two
Function Calls: A function call is an expression.
Precedence: How various operators nest.
Pattern Overview: What goes into a pattern.
Regexp Patterns: Using regexps as patterns.
Expression Patterns: Any expression can be used as a pattern.
Ranges: Pairs of patterns specify record ranges.
BEGIN/END: Specifying initialization and cleanup
Using BEGIN/END: How and why to use BEGIN/END rules.
I/O And BEGIN/END: I/O issues in BEGIN/END rules.
Empty: The empty pattern, which matches every
Using Shell Variables: How to use shell variables with
Action Overview: What goes into an action.
Statements: Describes the various control statements in
If Statement: Conditionally execute some `awk'
While Statement: Loop until some condition is satisfied.
Do Statement: Do specified action while looping until
For Statement: Another looping statement, that provides
Switch Statement: Switch/case evaluation for conditional
Break Statement: Immediately exit the innermost enclosing
Continue Statement: Skip to the end of the innermost enclosing
Next Statement: Stop processing the current input record.
Nextfile Statement: Stop processing the current file.
Exit Statement: Stop execution of `awk'.
Built-in Variables: Summarizes the built-in variables.
User-modified: Built-in variables that you change to
Auto-set: Built-in variables where `awk'
ARGC and ARGV: Ways to use `ARGC' and `ARGV'.
Array Intro: Introduction to Arrays
Reference to Elements: How to examine one element of an array.
Assigning Elements: How to change an element of an array.
Array Example: Basic Example of an Array
Scanning an Array: A variation of the `for' statement. It
Delete: The `delete' statement removes an
Numeric Array Subscripts: How to use numbers as subscripts in
Uninitialized Subscripts: Using Uninitialized variables as
Multi-dimensional: Emulating multidimensional arrays in
Multi-scanning: Scanning multidimensional arrays.
Array Sorting: Sorting array values and indices.
Built-in: Summarizes the built-in functions.
Calling Built-in: How to call built-in functions.
Numeric Functions: Functions that work with numbers, including
String Functions: Functions for string manipulation, such as
Gory Details: More than you want to know about `\'
I/O Functions: Functions for files and shell commands.
Time Functions: Functions for dealing with timestamps.
Bitwise Functions: Functions for bitwise operations.
I18N Functions: Functions for string translation.
User-defined: Describes User-defined functions in detail.
Definition Syntax: How to write definitions and what they
Function Example: An example function definition and what it
Function Caveats: Things to watch out for.
Return Statement: Specifying the value a function returns.
Dynamic Typing: How variable types can change at runtime.
I18N and L10N: Internationalization and Localization.
Explaining gettext: How GNU `gettext' works.
Programmer i18n: Features for the programmer.
Translator i18n: Features for the translator.
String Extraction: Extracting marked strings.
Printf Ordering: Rearranging `printf' arguments.
I18N Portability: `awk'-level portability issues.
I18N Example: A simple i18n example.
Gawk I18N: `gawk' is also internationalized.
Nondecimal Data: Allowing nondecimal input data.
Two-way I/O: Two-way communications with another
TCP/IP Networking: Using `gawk' for network
Portal Files: Using `gawk' with BSD portals.
Profiling: Profiling your `awk' programs.
Command Line: How to run `awk'.
Options: Command-line options and their meanings.
Other Arguments: Input file names and variable assignments.
AWKPATH Variable: Searching directories for `awk'
Obsolete: Obsolete Options and/or features.
Undocumented: Undocumented Options and Features.
Known Bugs: Known Bugs in `gawk'.
Library Names: How to best name private global variables
General Functions: Functions that are of general use.
Nextfile Function: Two implementations of a `nextfile'
Assert Function: A function for assertions in `awk'
Round Function: A function for rounding if `sprintf'
Cliff Random Function: The Cliff Random Number Generator.
Ordinal Functions: Functions for using characters as numbers
Join Function: A function to join an array into a string.
Gettimeofday Function: A function to get formatted times.
Data File Management: Functions for managing command-line data
Filetrans Function: A function for handling data file
Rewind Function: A function for rereading the current file.
File Checking: Checking that data files are readable.
Empty Files: Checking for zero-length files.
Ignoring Assigns: Treating assignments as file names.
Getopt Function: A function for processing command-line
Passwd Functions: Functions for getting user information.
Group Functions: Functions for getting group information.
Running Examples: How to run these examples.
Clones: Clones of common utilities.
Cut Program: The `cut' utility.
Egrep Program: The `egrep' utility.
Id Program: The `id' utility.
Split Program: The `split' utility.
Tee Program: The `tee' utility.
Uniq Program: The `uniq' utility.
Wc Program: The `wc' utility.
Miscellaneous Programs: Some interesting `awk' programs.
Dupword Program: Finding duplicated words in a document.
Alarm Program: An alarm clock.
Translate Program: A program similar to the `tr'
Labels Program: Printing mailing labels.
Word Sorting: A program to produce a word usage count.
History Sorting: Eliminating duplicate entries from a
Extract Program: Pulling out programs from Texinfo source
Simple Sed: A Simple Stream Editor.
Igawk Program: A wrapper for `awk' that includes
V7/SVR3.1: The major changes between V7 and System V
SVR4: Minor changes between System V Releases 3.1
POSIX: New features from the POSIX standard.
BTL: New features from the Bell Laboratories
POSIX/GNU: The extensions in `gawk' not in
Contributors: The major contributors to `gawk'.
Gawk Distribution: What is in the `gawk' distribution.
Getting: How to get the distribution.
Extracting: How to extract the distribution.
Distribution contents: What is in the distribution.
Unix Installation: Installing `gawk' under various
Quick Installation: Compiling `gawk' under Unix.
Additional Configuration Options: Other compile-time options.
Configuration Philosophy: How it's all supposed to work.
Non-Unix Installation: Installation on Other Operating Systems.
Amiga Installation: Installing `gawk' on an Amiga.
BeOS Installation: Installing `gawk' on BeOS.
PC Installation: Installing and Compiling `gawk' on
PC Binary Installation: Installing a prepared distribution.
PC Compiling: Compiling `gawk' for MS-DOS, Windows32,
PC Using: Running `gawk' on MS-DOS, Windows32 and
PC Dynamic: Compiling `gawk' for dynamic
Cygwin: Building and running `gawk' for
VMS Installation: Installing `gawk' on VMS.
VMS Compilation: How to compile `gawk' under VMS.
VMS Installation Details: How to install `gawk' under VMS.
VMS Running: How to run `gawk' under VMS.
VMS POSIX: Alternate instructions for VMS POSIX.
Unsupported: Systems whose ports are no longer
Atari Installation: Installing `gawk' on the Atari ST.
Atari Compiling: Compiling `gawk' on Atari.
Atari Using: Running `gawk' on Atari.
Tandem Installation: Installing `gawk' on a Tandem.
Bugs: Reporting Problems and Bugs.
Other Versions: Other freely available `awk'
Compatibility Mode: How to disable certain `gawk'
Additions: Making Additions To `gawk'.
Adding Code: Adding code to the main body of
New Ports: Porting `gawk' to a new operating
Dynamic Extensions: Adding new built-in functions to
Internals: A brief look at some `gawk'
Sample Library: A example of new functions.
Internal File Description: What the new functions will do.
Internal File Ops: The code for internal file operations.
Using Internal File Ops: How to use an external extension.
Future Extensions: New features that may be implemented one
Basic High Level: The high level view.
Basic Data Typing: A very quick intro to data types.
Floating Point Issues: Stuff to know about floating-point numbers.

To Miriam, for making me complete. To Chana, for the joy you bring us. To Rivka, for the exponential increase. To Nachum, for the added dimension. To Malka, for the new beginning.

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