Sundeep Agarwal - GNU GREP and RIPGREP

Sundeep Agarwal

You are likely to be familiar with using Ctrl+F from an editor, word processor, web browser, IDE, etc to quickly locate where a particular string occurs. grep is similar, but much more versatile and feature-rich version of the search functionality usable from the command line. Modern requirements have given rise to tools like ripgrep that provide out-of-box features such as recursive search while respecting ignore rules of a version controlled directory. An important feature that the GUI applications may lack is regular expressions, which helps to precisely define a matching criteria. You could consider it as sort of a mini-programming language in itself. So, apart from covering command options, regular expressions will also be discussed in detail in this book.

The book heavily leans on examples to present features one by one. It is recommended that you manually type each example and experiment with them. Understanding both the nature of sample input string and the output produced is essential. As an analogy, consider learning to drive a bike or a car no matter how much you read about them or listen to explanations, you need to practice a lot and infer your own conclusions. Should you feel that copy-paste is ideal for you, code snippets are available chapter wise on GitHub.

My Command Line Text Processing repository includes a chapter on GNU grep which has been edited and expanded to create this book.

Prior experience working with command line and bash shell, should know concepts like file redirection, command pipeline and so on.

If you are new to the world of command line, check out my curated resources on Linux CLI and Shell scripting before starting this book.

• The examples presented here have been tested on GNU bash shell with GNU grep 3.6 and ripgrep 12.1.1 and includes features not available in earlier versions.
• Code snippets shown are copy pasted from bash shell and modified for presentation purposes. Some commands are preceded by comments to provide context and explanations. Blank lines have been added to improve readability, only real time is shown for speed comparisons, output is skipped for commands like wget and so on.
• Unless otherwise noted, all examples and explanations are meant for ASCII characters.
• External links are provided for further reading throughout the book. Not necessary to immediately visit them. They have been chosen with care and would help, especially during re-reads.
• The learn_gnugrep_ripgrep repo has all the code snippets and files used in examples, exercises and other details related to the book. If you are not familiar with git command, click the Code button on the webpage to get the files.

• GNU grep documentation manual and examples
• ripgrep user guide and examples
• stackoverflow and unix.stackexchange for getting answers to pertinent questions on bash, grep and other commands
• tex.stackexchange for help on pandoc and tex related questions
• Cover image
  • LibreOffice Draw
  • detective by olarte.ollie under Creative Commons Attribution-Share Alike 2.0 Generic
• pngquant and svgcleaner for optimizing images
• softwareengineering.stackexchange and skolakoda for programming quotes
• Warning and Info icons by Amada44 under public domain
• Andrew Gallant (author of ripgrep) and mikeblas for critical feedback

Special thanks to all my friends and online acquaintances for their help, support and encouragement, especially during difficult times.

I would highly appreciate if you'd let me know how you felt about this book, it would help to improve this book as well as my future attempts. Also, please do let me know if you spot any error or typo.

Issue Manager: https://github.com/learnbyexample/learn_gnugrep_ripgrep/issues

E-mail:

Twitter: https://twitter.com/learn_byexample

Sundeep Agarwal is a freelance trainer, author and mentor. His previous experience includes working as a Design Engineer at Analog Devices for more than 5 years. You can find his other works, primarily focused on Linux command line, text processing, scripting languages and curated lists, at https://github.com/learnbyexample. He has also been a technical reviewer for Command Line Fundamentals book and video course published by Packt.

List of books: https://learnbyexample.github.io/books/

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License

Code snippets are available under MIT License

Resources mentioned in Acknowledgements section above are available under original licenses.

1.7

See Version_changes.md to track changes across book versions.

Quoting from wikipedia:

grep is a command-line utility for searching plain-text data sets for lines that match a regular expression. Its name comes from the ed command g/re/p (globally search a regular expression and print), which has the same effect.

Use of grep has become so ubiquitous that it has found its way into Oxford dictionary as well. As part of daily computer usage, searching comes up often. It could be finding the right emoji by their name on social media or using Ctrl+F in word processor/IDE/web browser/ebook/bookmarks/etc. Some of these have options to refine the search further like matching case, ignoring case, limiting to whole word, using regular expressions etc. grep provides all of these features and much more when it comes to searching or extracting content from text files. After getting used to grep, the search features provided by GUI programs often feel inadequate and slower.

If you are on a Unix like system, you are most likely to already have some version of grep installed. This book is primarily for GNU grep and also has a chapter on ripgrep. As there are syntax and feature differences between various implementations, please make sure to follow along with what is presented here.

GNU grep is part of text creation and manipulation commands provided by GNU and comes by default on GNU/Linux. To install newer or particular version, visit gnu: software and check release notes for an overview of changes between versions. See also bug list.

If you are not using a Linux distribution, you may be able to access GNU grep using below options:

• git-bash
• WSL
• brew

It is always a good idea to know where to find the documentation. From command line, you can use man grep for a short manual and info grep for full documentation. I prefer using the online gnu grep manual which feels much easier to use and navigate.

For a quick overview of all the available options, use grep --help from the command line. These are shown below in table format: