- Learning Linux Shell Scripting
- Table of Contents
- Learning Linux Shell Scripting
- Credits
- About the Author
- Acknowledgments
- About the Reviewers
- www.PacktPub.com
- Preface
- 1. Getting Started and Working with Shell Scripting
- 2. Drilling Deep into Process Management, Job Control, and Automation
- 3. Using Text Processing and Filters in Your Scripts
- 4. Working with Commands
- 5. Exploring Expressions and Variables
- 6. Neat Tricks with Shell Scripting
- Interactive Shell scripts – reading user input
- The here document and the << operator
- The here string and the <<< operator
- File handling
- Debugging
- Summary
- 7. Performing Arithmetic Operations in Shell Scripts
- 8. Automating Decision Making in Scripts
- Checking the exit status of commands
- Understanding the test command
- Conditional constructs – if else
- Switching case
- Implementing simple menus with select
- Looping with the for command
- Exiting from the current loop iteration with the continue command
- Exiting from a loop with a break
- Working with the do while loop
- Using until
- Piping the output of a loop to a Linux command
- Running loops in the background
- The IFS and loops
- Summary
- 9. Working with Functions
- 10. Using Advanced Functionality in Scripts
- 11. System Startup and Customizing a Linux System
- 12. Pattern Matching and Regular Expressions with sed and awk
- The basics of regular expressions
- sed – noninteractive stream editor
- Understanding sed
- Understanding regular expression usage in sed
- Addressing in sed
- How to modify a file with sed
- Printing – the p command
- Deleting – the d command
- Substitution – the s command
- Range of selected lines: the comma
- Multiple edits – the e command
- Reading from files – the r command
- Writing to files – the w command
- Appending – the a command
- Inserting – the i command
- Changing – the c command
- Transform – the y command
- Quit – the q command
- Holding and getting – the h and g commands
- Holding and exchanging – the h and x commands
- sed scripting
- Using awk
- The meaning of awk
- Using awk
- Input from commands
- How awk works
- awk commands from within a file
- Records and fields
- Patterns and actions
- Regular expressions
- Writing the awk script file
- Using variables in awk
- Decision making using an if statement
- Using the for loop
- Using the while loop
- Using the do while loop
- Summary
- Index
The here string is used for input redirection from text or a variable. Input is mentioned on the same line within single quotes ('').
The syntax is as follows:
$ command <<< 'string'
- Let's see the following example
hereString_01.sh:#!/bin/bash wc –w <<< 'Good Morning and have a nice day !'
- Save the file, give the permission, and run the script as follows:
$ chmod u+x hereString_01.sh $ ./hereString_01.sh
- Here is the output:
8
In this example, the string
Good Morning and have a nice day ! is called as the here string.
-
No Comment
..................Content has been hidden....................
You can't read the all page of ebook, please click here login for view all page.