Table of Contents for
Linux Shell Scripting Bootcamp

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Linux Shell Scripting Bootcamp by James Kent Lewis Published by Packt Publishing, 2017
  1. Cover
  2. Table of Contents
  3. Linux Shell Scripting Bootcamp
  4. Linux Shell Scripting Bootcamp
  5. Credits
  6. About the Author
  7. Acknowledgement
  8. About the Reviewer
  9. www.PacktPub.com
  10. Customer Feedback
  11. Preface
  12. What you need for this book
  13. Who this book is for
  14. Conventions
  15. Reader feedback
  16. Customer support
  17. 1. Getting Started with Shell Scripting
  18. Demonstrating the use of scripts
  19. Summary
  20. 2. Working with Variables
  21. Validating parameters using conditional statements
  22. Comparison operators for strings
  23. Environment variables
  24. Summary
  25. 3. Using Loops and the sleep Command
  26. Screen manipulation
  27. Indenting your code
  28. Using the for statement
  29. Leaving a loop early
  30. The sleep command
  31. Watching a process
  32. Creating numbered backup files
  33. Summary
  34. 4. Creating and Calling Subroutines
  35. File redirection
  36. Command piping
  37. Subroutines
  38. Using parameters
  39. Making a current backup of your work
  40. Summary
  41. 5. Creating Interactive Scripts
  42. Summary
  43. 6. Automating Tasks with Scripts
  44. Summary
  45. 7. Working with Files
  46. Reading files
  47. Reading and writing files
  48. Reading and writing files interactively
  49. File checksums
  50. File encryption
  51. Summary
  52. 8. Working with wget and curl
  53. wget and recursion
  54. wget options
  55. curl
  56. Summary
  57. 9. Debugging Scripts
  58. Automatic backups
  59. More syntax errors
  60. Logic errors
  61. Using set to debug scripts
  62. Summary
  63. 10. Scripting Best Practices
  64. ssh and scp
  65. Find and use a good text editor
  66. Environment variables and aliases
  67. ssh prompt
  68. Testing an archive
  69. Progress indicator
  70. Creating new commands from a template
  71. Alerting the user
  72. Summary
  73. Index

Command piping

Now let's look at command piping, which is the ability to run a command and have the output from it serve as the input to another command.

Suppose a program or script named loop1 is running on your system and you want to know the PID of it. You could run the ps auxw command to a file, and then grep the file for loop1. Alternatively, you could do it in one step by using a pipe as follows:

Command piping

Pretty cool, right? This is a very powerful feature in a Linux system and is used extensively. We will be seeing a lot more of this soon.

The next section shows another very short script using some command piping. This clears the screen and then shows only the first 10 lines from dmesg:

Chapter 4 - Script 2

#!/bin/sh
#
# 5/8/2017
#
tput clear
dmesg | head

And here is the output:

Chapter 4 - Script 2

The next section shows file redirection.

Chapter 4 - Script 3

#!/bin/sh
#
# 5/8/2017
#
FN=/tmp/dmesg.txt
dmesg > $FN
echo "File $FN created."
exit 0

Try it on your system.

This shows how easy it is to create a script to perform commands that you would normally type on the command line. Also notice the use of the FN variable. If you want to use a different filename later, you only have to make the change in one place.