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Linux Shell Scripting Essentials

Linux Shell Scripting Essentials

By : Sinny Kumari
4.5 (2)
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Linux Shell Scripting Essentials

Linux Shell Scripting Essentials

4.5 (2)
By: Sinny Kumari

Overview of this book

Shell scripting is a quick method to prototype complex applications or problems. Shell scripts are a collection of commands to automate tasks, usually those for which the user has a repeated need, when working on Linux-based systems. Using simple commands or a combination of them in a shell can solve complex problems easily. This book starts with the basics, including essential commands that can be executed on Linux systems to perform tasks within a few nanoseconds. You’ll learn to use outputs from commands and transform them to show the data you require. Discover how to write shell scripts easily, execute script files, debug, and handle errors. Next, you’ll explore environment variables in shell programming and learn how to customize them and add a new environment. Finally, the book walks you through processes and how these interact with your shell scripts, along with how to use scripts to automate tasks and how to embed other languages and execute them.
Table of Contents (10 chapters)
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9
Index

Special files


The files other than regular files, directories, and link files are special files. They are as follows:

  • The block device file

  • The character device file

  • The named pipe file

  • The socket file

The block device file

A block device file is a file that reads and writes data in block. Such files are useful when data needs to be written in bulk. Devices such as hard disk drive, USB drive, and CD-ROM are considered as block device files. Data is written asynchronously and, hence, other users are not blocked to perform the write operation at the same time.

To create a block device file, mknod is used with the option b along with providing a major and minor number. A major number selects which device driver is being called to perform the input and output operation. A minor number is used to identify subdevices:

$ sudo mknod  block_device b 0X7 0X6

Here, 0X7 is a major number and 0X6 is a minor number in hexadecimal format:

$ ls -l block_device
brw-r--r--. 1 root root 7, 6 Aug 24 12:21 block_device...

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