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)

Handling filenames starting with dashes

Recall that in any situation where a filename is stored in a variable, we must be careful when using it on a command line, because it might get interpreted as an option:

$ cp "$myvar" destdir

If myvar were a file named -alphabet-, this would result in a confusing error:

cp: invalid option -- 'h'

This is because the string was interpreted as a bundled set of options, and the letters a, l, and p are all valid options for the GNU cp command, but h is not.

We can address this one of two main ways; the first, for the commands that support it, is to use the -- terminator string option:

$ cp -- "$myvar" destdir

This signals to the cp command that every word after that argument is not an option, but (in this case) a file or directory name to operate on.

Unfortunately, while this is a very widespread convention, not...