Table of Contents for
Learning Linux Shell Scripting

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Learning Linux Shell Scripting by Ganesh Sanjiv Naik Published by Packt Publishing, 2015
  1. Cover
  2. Table of Contents
  3. Learning Linux Shell Scripting
  4. Learning Linux Shell Scripting
  5. Credits
  6. About the Author
  7. Acknowledgments
  8. About the Reviewers
  9. www.PacktPub.com
  10. Preface
  11. What you need for this book
  12. Who this book is for
  13. Conventions
  14. Reader feedback
  15. Customer support
  16. 1. Getting Started and Working with Shell Scripting
  17. Tasks done by shell
  18. Working in shell
  19. Learning basic Linux commands
  20. Our first script – Hello World
  21. Compiler and interpreter – difference in process
  22. When not to use scripts
  23. Various directories
  24. Working more effectively with shell – basic commands
  25. Working with permissions
  26. Summary
  27. 2. Drilling Deep into Process Management, Job Control, and Automation
  28. Monitoring processes using ps
  29. Process management
  30. Process monitoring tools – top, iostat, and vmstat
  31. Understanding "at"
  32. Understanding "crontab"
  33. Summary
  34. 3. Using Text Processing and Filters in Your Scripts
  35. IO redirection
  36. Pattern matching with the vi editor
  37. Pattern searching using grep
  38. Summary
  39. 4. Working with Commands
  40. Command substitution
  41. Command separators
  42. Logical operators
  43. Pipes
  44. Summary
  45. 5. Exploring Expressions and Variables
  46. Working with environment variables
  47. Working with read-only variables
  48. Working with command line arguments (special variables, set and shift, getopt)
  49. Understanding getopts
  50. Understanding default parameters
  51. Working with arrays
  52. Summary
  53. 6. Neat Tricks with Shell Scripting
  54. The here document and the << operator
  55. The here string and the <<< operator
  56. File handling
  57. Debugging
  58. Summary
  59. 7. Performing Arithmetic Operations in Shell Scripts
  60. Using the let command for arithmetic
  61. Using the expr command for arithmetic
  62. Binary, octal, and hex arithmetic operations
  63. A floating-point arithmetic
  64. Summary
  65. 8. Automating Decision Making in Scripts
  66. Understanding the test command
  67. Conditional constructs – if else
  68. Switching case
  69. Implementing simple menus with select
  70. Looping with the for command
  71. Exiting from the current loop iteration with the continue command
  72. Exiting from a loop with a break
  73. Working with the do while loop
  74. Using until
  75. Piping the output of a loop to a Linux command
  76. Running loops in the background
  77. The IFS and loops
  78. Summary
  79. 9. Working with Functions
  80. Passing arguments or parameters to functions
  81. Sharing the data by many functions
  82. Declaring local variables in functions
  83. Returning information from functions
  84. Running functions in the background
  85. Creating a library of functions
  86. Summary
  87. 10. Using Advanced Functionality in Scripts
  88. Using the trap command
  89. Ignoring signals
  90. Using traps in function
  91. Running scripts or processes even if the user logs out
  92. Creating dialog boxes with the dialog utility
  93. Summary
  94. 11. System Startup and Customizing a Linux System
  95. User initialization scripts
  96. Summary
  97. 12. Pattern Matching and Regular Expressions with sed and awk
  98. sed – noninteractive stream editor
  99. Using awk
  100. Summary
  101. Index

Our first script – Hello World

Since we learned basic commands to use Linux OS, we will now write our first Shell script called hello.sh. You can use any editor of your choice such as vi, gedit, nano, and other similar editors. I prefer to use the vi editor.

  1. Create a new hello.sh file as follows:
    #!/bin/bash
# This is comment line
echo "Hello World"
ls
date
  2. Save the newly created file.

The #!/bin/bash line is called the shebang line. The combination of the characters # and ! is called the magic number. The shell uses this to call the intended shell such as /bin/bash in this case. This should always be the first line in a Shell script.

The next few lines in the Shell script are self explanatory.

  • Any line starting with #, will be treated as a comment line. An exception to this would be the first line with #!/bin/bash
  • The echo command will print Hello World on the screen
  • The ls command will display directory content on the console
  • The date command will show the current date and time

We can execute the newly created file by the following commands:

  • Technique one:
    $ bash hello.sh
  • Technique two:
    $ chmod +x hello.sh

By running any of the preceding commands, we are adding executable permission to our newly created file. You will learn more about file permissions in later in this same chapter.

$ ./hello.sh

By running the preceding command, we are executing hello.sh as the executable file. By technique one, we passed filename as an argument to Bash shell.

The output of executing hello.sh will be as follows:

Hello World
hello.sh
Sun Jan 18 22:53:06 IST 2015

Since we have successfully executed our first script, we will proceed to develop a more advanced script, hello1.sh. Please create the new script hello.sh as follows:

#!/bin/bash
# This is the first Bash shell
# Scriptname : Hello1.sh
# Written by:  Ganesh Naik
echo "Hello $LOGNAME, Have a nice day !"
echo "Your are working in directory `pwd`."
echo "You are working on a machine called `uname -n`."
echo "List of files in your directory is."
ls      # List files in the present working directory
echo  "Bye for now $LOGNAME. The time is `date +%T`!"

The output of executing hello.sh will be as follows:

Hello student, Have a nice day !.
Your are working in directory /home/student/work.
You are working on a machine called ubuntu.
List of files in your directory is.
hello1.sh  hello.sh
Bye for now student. The time is 22:59:03!

You will learn about the LOGNAME, uname, and other similar commands as we go on with the book.