Book Image

Linux Essentials - Second Edition

By : Christine Bresnahan, Richard Blum
Book Image

Linux Essentials - Second Edition

By: Christine Bresnahan, Richard Blum

Overview of this book

Linux Essentials, Second Edition provides a solid foundation of knowledge for anyone considering a career in information technology, for anyone new to the Linux operating system, and for anyone who is preparing to sit for the Linux Essentials Exam. Through this engaging resource, you can access key information in a learning-by-doing style. Hands-on tutorials and end-of-chapter exercises and review questions lead you in both learning and applying new information—information that will help you achieve your goals! With the experience provided in this compelling reference, you can sit down for the Linux Essentials Exam with confidence. An open-source operating system, Linux is a UNIX-based platform that is freely updated by developers. The nature of its development means that Linux is a low-cost and secure alternative to other operating systems, and is used in many different IT environments. Passing the Linux Essentials Exam prepares you to apply your knowledge regarding this operating system within the workforce.
Table of Contents (19 chapters)
17
EULA

Beginning a Shell Script

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Shell scripts are plain-text files, so you create them in text editors such as vi, nano, or pico, as described in Chapter 10, “Editing Files.” A shell script begins with a line that identifies the shell that’s used to run it, such as the following:

#!/bin/bash

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The first two characters are a special code that tells the Linux kernel that this is a script and to use the rest of the line as a pathname to the program that’s to interpret the script. (This line is sometimes called the shebang, hashbang, hashpling, or pound bang line.) Shell scripting languages use a hash mark (#) as a comment character, so the script utility ignores this line, although the kernel doesn’t. On most systems, /bin/sh is a symbolic link that points to /bin/bash, but it can point to another shell. Specifying the script as using /bin/sh guarantees that any Linux system will have a shell program to run the script. However, if the script uses any features...