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Linux Shell Scripting Essentials

You're reading from   Linux Shell Scripting Essentials Learn shell scripting to solve complex shell-related problems and to efficiently automate your day-to-day tasks

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Product type Paperback
Published in Nov 2015
Publisher
ISBN-13 9781785284441
Length 282 pages
Edition 1st Edition
Tools
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Toc

Table of Contents (10) Chapters Close

Preface 1. The Beginning of the Scripting Journey FREE CHAPTER 2. Getting Hands-on with I/O, Redirection Pipes, and Filters 3. Effective Script Writing 4. Modularizing and Debugging 5. Customizing the Environment 6. Working with Files 7. Welcome to the Processes 8. Scheduling Tasks and Embedding Languages in Scripts Index

Process management


Managing processes is very important because processes are what consumes system resources. System users should be careful about the processes they are creating, in order to ensure that a process is not affecting any other critical processes.

Process creation and execution

In bash, creating a process is very easy. When a program is executed, a new process is created. In a Linux or Unix-based system, when a new process is created, a unique ID is assigned to it, which is known as PID. A PID value is always a positive number starting from 1. Depending upon a system having init or systemd, they always get the PID value 1 because this will be the first process in a system and it is the ancestor of all other processes.

The maximum value of PID is defined in the pid_max file, which should be available in the /proc/sys/kernel/ directory. By default, the pid_max file contains the value 32768 (max PID + 1), which means a maximum of 32767 processes can exist in a system simultaneously...

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