Book Image

Learning AWK Programming

By : Shiwang Kalkhanda
5 (1)
Book Image

Learning AWK Programming

5 (1)
By: Shiwang Kalkhanda

Overview of this book

AWK is one of the most primitive and powerful utilities which exists in all Unix and Unix-like distributions. It is used as a command-line utility when performing a basic text-processing operation, and as programming language when dealing with complex text-processing and mining tasks. With this book, you will have the required expertise to practice advanced AWK programming in real-life examples. The book starts off with an introduction to AWK essentials. You will then be introduced to regular expressions, AWK variables and constants, arrays and AWK functions and more. The book then delves deeper into more complex tasks, such as printing formatted output in AWK, control flow statements, GNU's implementation of AWK covering the advanced features of GNU AWK, such as network communication, debugging, and inter-process communication in the GAWK programming language which is not easily possible with AWK. By the end of this book, the reader will have worked on the practical implementation of text processing and pattern matching using AWK to perform routine tasks.

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Table of Contents (11 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Get in touch
Free Chapter
1
Getting Started with AWK Programming
Getting Started with AWK Programming
AWK programming language overview
Getting started with AWK
AWK standard options
Summary
2
Working with Regular Expressions
Working with Regular Expressions
Introduction to regular expressions
Basic regular expression construct
Understanding regular expression metacharacters
Precedence in regular expressions
GAWK-specific regular expression operators
Case-sensitive matching
Escape sequences
Summary
3
AWK Variables and Constants
AWK Variables and Constants
Built-in variables in AWK
Environment variables in AWK
Environment variables in GAWK
String constants
Numeric constants
Conversion between strings and numbers
Summary
4
Working with Arrays in AWK
Working with Arrays in AWK
One-dimensional arrays
Assignment in arrays
Accessing elements in arrays
Referring to members in arrays
Processing arrays using loops
Using the split() function to create arrays
Delete operation in arrays
Multidimensional arrays
Summary
5
Printing Output in AWK
Printing Output in AWK
The print statement
Role of output separator in print statement
Pretty printing with the printf statement
Escape sequences for special character printing
Different format control characters in the format specifier
Format specification modifiers
Redirecting output to file
Summary
6
AWK Expressions
AWK Expressions
AWK variables and constants
Arithmetic expressions using binary operators
Assignment expressions
Increment and decrement expressions
Relational expressions
Logical or Boolean expressions
Ternary expressions
Unary expressions
Exponential expressions
String concatenation
Regular expression operators
Operators' Precedence
Summary
7
AWK Control Flow Statements
AWK Control Flow Statements
Conditional statements
Looping statement
Statements affecting flow control
Summary
8
AWK Functions
AWK Functions
Built-in functions
User-defined functions
Summary
9
GNU's Implementation of AWK – GAWK (GNU AWK)
GNU's Implementation of AWK – GAWK (GNU AWK)
Things you don't know about GAWK
Summary
10
Practical Implementation of AWK
Practical Implementation of AWK
Working with one-liners for text processing and pattern matching with AWK
Use case examples of pattern matching using AWK
Summary
Further reading

Who this book is for

The book is written from the beginners' point of view. It covers the basic to intermediate skills that are essential for text processing in a simple and effective manner. But at the same time, there is good amount of stuff that a seasoned AWK user shall find interesting. It covers a wide range of audience and shall be useful to the following people:

  • Data scientists who need to extract and clean data for analysis
  • Developers who perform parsing of flat text files, HTML files, XML files, or CSV files
  • System administrators who parse log files for analysis
  • Any GNU/Linux hobbyist or enthusiast who likes to play with GNU/Linux filters for data manipulation

It is written in such a manner that any user with a basic familiarity with the GNU/Linux command line can start using it. The only requisite for it is to have a GNU/Linux box for practicing the stuff covered. This book begins with the essentials of text processing, that is, regular expressions (followed by the structure of the AWK program), variables, constants, functions, arrays, printing options, control flow of the program, and use of different operators to carry out various text processing and mining tasks.

For advanced users, Chapter 9, GNU's Implementation of AWK – GAWK (GNU AWK), covers GAWK implementation in networking, inter-process communication, and debugging. It is followed by practical examples for text processing and pattern matching. For system administrators, we have covered quick one liners that they will find useful in their daily operations. This book has got something for every learner who is working on GNU/Linux.

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