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)

Using globs

A * unquoted asterisk character on a command line has a special meaning to Bash: it means it should expand the word in which the character occurs to all of the matching filenames if possible, but (by default) to leave the word unchanged if there are no such matching files.

This can be confusing, and is best explained with a few examples. Suppose our current directory has the following filenames:

$ ls -a
.  ..  .bashrc  april  august  october  september

A glob by itself will expand to all the filenames that are not prefixed with a dot:

$ printf '%s\n' *

Note that the filenames are expanded in alphabetical order or, more correctly, the order specified by your language environment's collation settings.

If there are other letters in the same word as a glob, they have to match the relevant filenames in the same position...