Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By : Richard Blum, Christine Bresnahan
Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By: Richard Blum, Christine Bresnahan

Overview of this book

The Linux command line enables you to type specific shell commands directly into the system to manipulate files and query system resources. Command line statements can be combined into short programs called shell scripts, a practice increasing in popularity due to its usefulness in automation. Linux is a robust system with tremendous potential, and Linux Command Line and Shell Scripting Bible opens the door to new possibilities. Linux Command Line and Shell Scripting Bible is your essential Linux guide. It contains new functional examples that are fully updated to align with the latest Linux features. Beginning with command line fundamentals, the book moves into shell scripting and shows you the practical application of commands in automating frequently performed functions. This book is a complete guide providing detailed instruction and expert advice working within this aspect of Linux. Whether used as a tutorial or as a quick reference, this book contains information that every Linux user should know.
Table of Contents (34 chapters)
Part I: The Linux Command Line
Part II: Shell Scripting Basics
Part III: Advanced Shell Scripting
Part IV: Creating Practical Scripts
End User License Agreement

Exploring Shell Types

The shell program that the system starts depends on your user ID configuration. In the /etc/passwd file, the user ID has its default shell program listed in field #7 of its record. The default shell program is started whenever the user logs into a virtual console terminal or starts a terminal emulator in the GUI.

In the following example, user christine has the GNU bash shell as her default shell program:

$ cat /etc/passwd
Christine:x:501:501:Christine B:/home/Christine:/bin/bash

The bash shell program resides in the /bin directory. A long listing reveals /bin/bash (the bash shell) is an executable program:

$ ls -lF /bin/bash
-rwxr-xr-x. 1 root root 938832 Jul 18  2013 /bin/bash*

Several other shell programs are on this particular CentOS distribution. They include tcsh, which is based off the original C shell:

$ ls -lF /bin/tcsh
-rwxr-xr-x. 1 root root 387328 Feb 21  2013 /bin/tcsh*

Also, the Debian based version of the ash shell, dash, is included: