Book Image

Learning Linux Shell Scripting

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting

By: Ganesh Sanjiv Naik

Overview of this book

Linux is the one of the most powerful and universally adopted OSes. Shell is a program that gives the user direct interaction with the operating system. Scripts are collections of commands that are stored in a file. The shell can read this file and act on the commands as if they were typed on the keyboard. Shell scripting is used to automate day-to-day administration, and for testing or product development tasks. This book covers Bash, GNU Bourne Again SHell, preparing you to work in the exciting world of Linux shell scripting. We start with an introduction to the Shell environment and explain basic commands used in Shell. Next we move on to check, kill, and control the execution of processes in Linux OS. Further, we teach you about the filter tools available in Linux and explain standard output and standard errors devices. Then we will ensure you understand Shell’s interpretation of commands and get a firmer grasp so you use them in practice. Next, you’ll experience some real-world essentials such as debugging and perform Shell arithmetic fluently. Then you’ll take a step ahead and learn new and advanced topics in Shell scripting, such as starting up a system and customizing a Linux system. Finally, you’ll get to understand the capabilities of scripting and learn about Grep, Stream Editor, and Awk.
Table of Contents (20 chapters)
Learning Linux Shell Scripting
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

When not to use scripts


Shell scripts have certain advantages over compiler-based programs, such as C or C++ language. However, Shell scripting has certain limitations as well.

The following are the advantages:

  • Scripts are easy to write

  • Scripts are quick to start and easy for debugging

  • They save the time of development.

  • Tasks of administration are automated

  • No additional setup or tools are required for developing or testing Shell script

The following are the limitations of Shell scripts:

  • Every line in Shell script creates a new process in the operating system. When we execute the compiled program such as C program, it runs as a single process for the complete program.

  • Since every command creates a new process, Shell scripts are slow as compared to compiled programs.

  • Shell scripts are not suitable if heavy math operations are involved.

  • There are Problems with cross-platform portability.

  • We cannot use Shell scripts in the following situations when:

    • Extensive file operations are required

    • We need data structures, such as linked lists or trees

    • We need to generate or manipulate graphics or GUIs

    • We need direct access to system hardware

    • We need a port or socket I/O

    • We need to use libraries or interface with legacy code

    • Proprietary, closed source applications are used (Shell scripts put the source code right out in the open for the entire world to see)