Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Overview of this book

The shell remains one of the most powerful tools on a computer system — yet a large number of users are unaware of how much one can accomplish with it. Using a combination of simple commands, we will see how to solve complex problems in day to day computer usage.Linux Shell Scripting Cookbook, Second Edition will take you through useful real-world recipes designed to make your daily life easy when working with the shell. The book shows the reader how to effectively use the shell to accomplish complex tasks with ease.The book discusses basics of using the shell, general commands and proceeds to show the reader how to use them to perform complex tasks with ease.Starting with the basics of the shell, we will learn simple commands with their usages allowing us to perform operations on files of different kind. The book then proceeds to explain text processing, web interaction and concludes with backups, monitoring and other sysadmin tasks.Linux Shell Scripting Cookbook, Second Edition serves as an excellent guide to solving day to day problems using the shell and few powerful commands together to create solutions.
Table of Contents (16 chapters)
Linux Shell Scripting Cookbook
About the Authors
About the Reviewers

Calculating the execution time for a command

While testing an application's efficiency or comparing different algorithms to solve a given problem, the execution time taken is very critical. A good algorithm should execute in a minimum amount of time. Let's see how to calculate the execution time.

How to do it...

  1. To measure the execution time, just prefix time to the command you want to run.

    For example:

    $ time COMMAND

    The command will execute and its output will be shown. Along with the output, the time command appends the time taken in stderr. An example is as follows:

    $ time ls
    real    0m0.008s
    user    0m0.001s
    sys     0m0.003s

    It will show real, user, and system times for execution.


    An executable binary of the time command is available at /usr/bin/time, as well as a shell built-in named time exists. When we run time, it calls the shell built-in by default. The shell built-in time has limited options. Hence, we should use an absolute path for the executable (/usr/bin...