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

Changing Security Settings

If you've already created a file or directory and need to change the security settings on it, Linux has a few different utilities available for this. This section shows you how to change the existing permissions, the default owner, and the default group settings for a file or directory.

Changing permissions

The chmod command allows you to change the security settings for files and directories. The format of the chmod command is:

 chmod options mode file

The mode parameter allows you to set the security settings using either octal or symbolic mode. The octal mode settings are pretty straightforward; just use the standard three-digit octal code you want the file to have:

 $ chmod 760 newfile
 $ ls -l newfile
 -rwxrw----    1 rich     rich            0 Sep 20 19:16 newfile

The octal file permissions are automatically applied to the file indicated. The symbolic mode permissions are not so easy to implement.

Instead of using the normal string of three sets...