Book Image

Bash Quick Start Guide

By : Tom Ryder
Book Image

Bash Quick Start Guide

By: Tom Ryder

Overview of this book

Bash and shell script programming is central to using Linux, but it has many peculiar properties that are hard to understand and unfamiliar to many programmers, with a lot of misleading and even risky information online. Bash Quick Start Guide tackles these problems head on, and shows you the best practices of shell script programming. This book teaches effective shell script programming with Bash, and is ideal for people who may have used its command line but never really learned it in depth. This book will show you how even simple programming constructs in the shell can speed up and automate any kind of daily command-line work. For people who need to use the command line regularly in their daily work, this book provides practical advice for using the command-line shell beyond merely typing or copy-pasting commands into the shell. Readers will learn techniques suitable for automating processes and controlling processes, on both servers and workstations, whether for single command lines or long and complex scripts. The book even includes information on configuring your own shell environment to suit your workflow, and provides a running start for interpreting Bash scripts written by others.
Table of Contents (10 chapters)

Choosing when to apply Bash

There are some tasks for which shell scripting in general, and Bash in particular, are especially well-suited:

  • Prototyping: Short Bash programs are quick and easy to write. It's quite common to "hack together" a simple script in Bash for later replacement by a script or program in a more advanced programming language that requires more effort to write and maintain.

  • Interactive system administration: A Bourne-style shell is assumed in very many contexts in Unix, and almost all of the system documentation you read will tell you to issue commands in a Bourne-style shell. This makes it a natural choice for a scripting language.

  • Automation: If you have a set of commands you often run together, making a script for them is as simple as writing them all into a text file, each on a new line, and making that file executable.

  • Connecting programs together: Like all Shell scripting languages, Bash specializes in moving data to and from files and between processes. Many programs are designed to work together in this way.

  • Filtering and transforming text input: Some programs, however, aren't designed to cooperate in this way, and they require some data filtering and transformation in the middle. Bash can be a very convenient language for doing this, and it's also a good language to call other tools such as awk or sed to do it for you.

  • Navigating the Unix filesystem: In Bash, it does not require much code to navigate and iterate through the filesystem, discovering, filtering, and processing files within it at runtime. Coupled with the find tool, especially a high-powered version such as GNU find, a lot can be done in a pattern over a filesystem with relatively little code.

  • Basic pattern-matching on strings: Bash has features that make it good for basic pattern-matching on strings, especially filenames and path names, with parameter expansion.

  • Portability: Bash works on and is packaged for a huge variety of Unix-like systems. POSIX shell script is even more widely supported. If you need to know your script and its runtime will remain portable to many Unix-like systems, Bash might be a good choice.