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Mastering Bash

You're reading from   Mastering Bash A Step-by-Step Guide to working with Bash Programming and Shell Scripting

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Product type Paperback
Published in Jun 2017
Publisher Packt
ISBN-13 9781784396879
Length 502 pages
Edition 1st Edition
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Author (1):
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Giorgio Zarrelli Giorgio Zarrelli
Author Profile Icon Giorgio Zarrelli
Giorgio Zarrelli
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Toc

Table of Contents (15) Chapters Close

Preface 1. Let's Start Programming FREE CHAPTER 2. Operators 3. Testing 4. Quoting and Escaping 5. Menus, Arrays, and Functions 6. Iterations 7. Plug into the Real World 8. We Want to Chat 9. Subshells, Signals, and Job Controls 10. Lets Make a Process Chat 11. Living as a Daemon 12. Remote Connections over SSH 13. Its Time for a Timer 14. Time for Safety

DEMO

So, how could we turn one of our scripts into a daemon? One first attempt could be using &. The trailing ampersand is a Bash built-in which instructs the shell to run the command in the background inside a subshell. Once the command is executed, the shell does not wait for it to finish but returns a code 0, which means successful, and proceeds further in any other commands that are to be executed:

zarrelli:~$ ls -lah & ps -jf
[1] 13704
total 48K
drwxr-xr-x 4 zarrelli zarrelli 4.0K Apr 12 14:12 .
drwxr-xr-x 4 zarrelli zarrelli 4.0K Apr 12 19:37 ..
-rw-r--r-- 1 zarrelli zarrelli 11 Apr 10 09:20 controller
-rwxr--r-- 1 zarrelli zarrelli 121 Apr 11 18:30 coproc.sh
-rwxr--r-- 1 zarrelli zarrelli 961 Apr 11 12:19 environment.sh
-rwxr--r-- 1 zarrelli zarrelli 382 Apr 11 10:08 looping.sh
-rw-r--r-- 1 zarrelli zarrelli 0 Apr 10 09:20 myfile.txt
-rw-r--r-- 1 zarrelli zarrelli 122 Apr...
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