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Linux Shell Scripting Cookbook, Second Edition

You're reading from   Linux Shell Scripting Cookbook, Second Edition Don't neglect the shell ‚Äì this book will empower you to use simple commands to perform complex tasks. Whether you're a casual or advanced Linux user, the cookbook approach makes it all so brilliantly accessible and, above all, useful.

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Product type Paperback
Published in May 2013
Publisher Packt
ISBN-13 9781782162742
Length 384 pages
Edition 2nd Edition
Tools
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Toc

Table of Contents (16) Chapters Close

Linux Shell Scripting Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
1. Shell Something Out FREE CHAPTER 2. Have a Good Command 3. File In, File Out 4. Texting and Driving 5. Tangled Web? Not At All! 6. The Backup Plan 7. The Old-boy Network 8. Put on the Monitor's Cap 9. Administration Calls Index

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

    Note that it is negative M.

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

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