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Learning Linux Shell Scripting. - Second Edition

You're reading from  Learning Linux Shell Scripting. - Second Edition

Product type Book
Published in May 2018
Publisher Packt
ISBN-13 9781788993197
Pages 332 pages
Edition 2nd Edition
Languages
Author (1):
Ganesh Sanjiv Naik Ganesh Sanjiv Naik
Profile icon Ganesh Sanjiv Naik

Table of Contents (17) Chapters

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 7. Performing Arithmetic Operations in Shell Scripts 8. Automating Decision-Making in Scripts 9. Automating Repetitive Tasks 10. Working with Functions 11. Using Advanced Functionality in Scripts 12. System Startup and Customizing a Linux System 13. Pattern Matching and Regular Expressions with sed and awk 14. Taking Backup and Embedding Other Languages in Shell Scripts 15. Database Administration Using Shell Scripts 16. Other Books You May Enjoy

Using traps inside a function

If we use the trap command inside a function in the script, then the reassigned signal behavior will become global inside a script. We can check this effect in the following script example.

Let's write shell script trap_01.sh as follows:

#!/bin/bash 
trap "echo  caught signal SIGINT" SIGINT 
trap "echo  caught signal SIGQUIT" 3 
trap "echo  caught signal SIGTERM" 15 
while : 
do 
    sleep 50 
done 

Let's test the program as follows:

    $ chmod +x trap_01.sh
    $ ./trap_01.sh

Output:

    ^Ccaught signal SIGINT
    ^Quit (core dumped)
    caught signal SIGQUIT

Let's write one more trap_02.sh shell script as follows:

#!/bin/bash 
 
trap "echo  caught signal SIGINT" SIGINT 
trap "echo  caught signal SIGQUIT" 3 
trap "echo  caught signal SIGTERM" 15 
trap "echo  caught signal...
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