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

Using head and tail for printing the last or first 10 lines

When looking into a large file, which consists of thousands of lines, we will not use a command such as cat to print the entire file contents. Instead we look for a sample (for example, the first 10 lines of the file or the last 10 lines of the file). We may need to print the first n lines or last n lines and even print all the lines except the last n lines or all lines except first n lines.

Another use case is to print lines from mth to nth lines.

The commands head and tail can help us do this.

How to do it...

The head command always reads the header portion of the input file.

  1. Print the first 10 lines as follows:

    $ head file
  2. Read the data from stdin as follows:

    $ cat text | head
  3. Specify the number of first lines to be printed as follows:

    $ head -n 4 file

    This command prints four lines.

  4. Print all lines excluding the last M lines as follows:

    $ head -n -M file


    Note that it is negative M.

    For example, to print all the lines except the...