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Learning Linux Shell Scripting

Learning Linux Shell Scripting

By : Ganesh Sanjiv Naik
3 (6)
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Learning Linux Shell Scripting

Learning Linux Shell Scripting

3 (6)
By: Ganesh Sanjiv Naik

Overview of this book

Linux is the most powerful and universally adopted OS. 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 reads this file and acts on commands as if they were typed on the keyboard. Learning Linux Shell Scripting covers Bash, GNU Bourne Again Shell, preparing you to work in the exciting world of Linux shell scripting. CentOS is a popular rpm-based stable and secured Linux distribution. Therefore, we have used CentOS distribution instead of Ubuntu distribution. Linux Shell Scripting is independent of Linux distributions, but we have covered both types of distros. We start with an introduction to the Shell environment and basic commands used. Next, we explore process management in Linux OS, real-world essentials such as debugging and perform Shell arithmetic fluently. You'll then take a step ahead and learn new and advanced topics in Shell scripting, such as decision making, starting up a system, and customizing a Linux environment. You will also learn about grep, stream editor, and AWK, which are very powerful text filters and editors. Finally, you'll get to grips with taking backup, using other language scripts in Shell Scripts as well as automating database administration tasks for MySQL and Oracle. By the end of this book, you will be able to confidently use your own shell scripts in the real world.
Table of Contents (17 chapters)
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Floating-point arithmetic

In the Bash shell, we can only perform integer arithmetic. If we want to perform arithmetic involving a floating point or fractional values, then we will need to use various other utilities, such as awk, bc, and similar.

Let's see an example of using the utility called bc:

    $ echo "scale=2; 15 / 2" | bc
    7.50
  

For using the bc utility, we need to configure a scale parameter. Scale is the number of significant digits to the right of the decimal point. We have told the bc utility to calculate 15 / 2, and then display the result with the scale of 2.

Another example is the following:

    $ bc
    ((83.12 + 32.13) * 37.3)
    4298.82
  

Many things can be done with the bc utility, such as all types of arithmetic operations including binary and unary operations; it has many defined mathematical functions. It has its own programming syntax...

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