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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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Table of Contents (15) Chapters Close

Preface 1. Let's Start Programming 2. Operators FREE CHAPTER 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

Signals

In the early days of computing, signals were a means to deal with unusual events, and usually, their job was to reset a condition to a default state. Nowadays, with facilities such as job control, signals are used to actually instruct processes on what to do and are now more an interprocess facilities than a reset mechanism, as they were originally conceived. Each signal is associated to an action that must be performed by the process receiving it, so here is a brief list with some of the more interesting signals that the kernel can send to a process:

  • SIGCHLD: This signal is sent to a parent process when a child terminates or stops.
  • SIGCONT: This tells the process that has been put on hold by SIGSTOP or SGSTP to resume its execution. These three signals are used in job controlling.
  • SIGHUP: This signal is sent to a process when its terminal is closed and kills it. It owes...
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