Bourne Again Shell (Bash): the improved shells of Bourne Shell

Bash or Bourne Again Shell is an improved and free version of Bourne Shell. This command processor will allow you to insert commands to generate multiple actions.

Table of contents

What is Bash?

Activated in a text window, Bash allows to command actions from a file. This file can be called “script”. This free Unix Shell can handle various operations such as file naming generics, piping, listening functions inside documents, command execution, control structures for condition evaluations and iteration.

Enhanced to conform to the Shell standard in the IEEE POSIX (Portable Operating system Interface) framework, it is released under the GNU license. Bash is also available for Unix and Linux versions, and soon in MS-DOS and Windows versions.

What justifies the name Bourne Again Shell?

First of all, it is an open source version of Bourne Shell. Secondly, the translation of Bourne Again Shell means the “rebirth”. But this nomination also communicates the combination of features sh, csh and ksh.

The Unix Shell interprets commands that provides basic users with an interface. From the command window, the user can communicate with the system. Bash opens a path for Unix users to control the internal components of operating systems through text.

It should also be noted that Bash has many extensions. It can run on various Unix-like operating systems like Linux and Mac OS X. On Windows, via SUA and by POSIX emulation thanks to Cygwin or MSYS. It is obviously available on MS-DOS.

The shell in computing

Shell refers to a program that provides access to the components of a computer operating system. Thanks to the shell, the core of the system is accessed while the shell determines the limit between the interior and the exterior of the system.

CLIs or command line interface shells

They provide a clear and efficient way to interact with the operating system without necessarily going through a graphical interface.

GUI or graphical user interface shells

Like macOS and Windows, these shells are more adapted to beginners. They are also available through CLIs but are just as available for more experienced users who want to interact at a command prompt.

What is the use of Bash?

Bash facilitates the manipulation of computer applications. When dealing with many files and multiple data, Bash makes it possible to specify commands for searching, sorting and processing of all kinds.

Those who use Bash the most are the system administrators. Bash is a real tool to help with failures and errors and is appreciated by system administrators. It allows to solve problems, errors by connecting to systems, configuration and networks.

Next come, software developers who use it for development tasks. Bash also facilitates code insertion, modification and testing of software.

The network engineers use Bash for all network-related tasks: testing, configuration, performance optimization on networks.

The researchers in computer science use it for the management of operating systems and to facilitate research on these systems.

The less regular and pro users use it according to their level of mastery. For all operations within the system, to launch programs and to maintain its own systems, Bash is used.

How does Bash work?

Bash works as a platform for command and execution of programs. On the basis of a shell script, inputs and outputs are activated in a corresponding way.

For example, a basic Bash command: list the contents of directories. This command allows to find the names of files and subdirectories in the working directory.

On the other hand, Bash also allows commands to be combined by channeling the output of one command as the input to another command. Using the -R parameter, one can list all the files in a file system. The answer will then be difficult for the human brain to understand. Channels are used to direct the output of the ls command to the Bash command: grep.

Thanks to the vertical bar ” | “, the directory listing outputs to the grep command to present the files and subdirectories that match the specified pattern.

The Bash command line facilitates various operations such as managing files and directories, checking network configuration… It is also possible to perform file modifications and demonstration of the difference between modified files.

Bash command types

There are simple commands, pipes, lists and compound commands. Simple commands are executed individually or in parallel with variables. Pipes allow the output of one or more commands to be executed as input to other commands. Lists execute several commands in a chain. And finally, compound commands are used to program scripts. At this point, commands can include loops and conditional constructs.

Bash also allows you to keep a history of commands by pressing the up arrow key. This reiterates the reexecution of a command.

The advantages and disadvantages of Bourne Again Shell

Bourne Again Shell is an improved version of Bourne Shell. It must therefore necessarily have some advantages compared to its first version.

Just like the others GNU projectsBash was initiated for a better use of software. It allows to preserve, to optimize the freedom of use, the studies, the copy and of course the modification of software. Bash emphasizes the creative work of users.

The advantages of shell scripts

They allow the automation of operations and the execution of a sequence of commands at once. Bash is generally easy to use for both beginners and experienced users. And it is available on any support no matter what Unix-like operating system without any modification.

Bash is also today considered to be the standard shell. Literature is available on this subject. On the other hand, compared to the C Shell, Bourne Shell has a richer programming language.

The usefulness of Shell scripts

The main use of shell scripts is to program commands in strings. The system will then execute them as a scripted event like batch files. On the other hand, shells also allow to substitute certain commands.

The difference between Bourne Again Shell and Bourne Shell

Shells allow you to execute commands from the keyboard to operating systems. However, some differences exist between Bash Bourne Again Shell and Bourne Shell.

The most popular shell is Bash, there are others such as Korn, C, tcsh and Zsh. But Bash is the standard shell of the Linux operating system. To find out what shells are available on your Linux, you can type the following command: chat/etc/marmites and you will get for example the following list: /bin/sh; /bin/bash; /bin/rbash; /bin/rbash.

What is the real difference between Bourne Shell and Bourne Shell Again?

Bash (Bourne Again Shell) is a version of Bourne Shell with more features. However, on the interface and the compatibility of the scripts, there are some differences.

The interface

Bourne Shell does not have all the amenities of Bash. Bourne Again Shell is more diversified on the colors of files. On Bourne Shell, blue directories are represented by text on a shaded background. On Bash, the directories are in blue, the binary files in burgundy, the non-binary ones are with the choice: black or white or according to your terminal.

Script compatibility

When you type a Bourne shell script, on a Bash shell, this command will be able to run without modification. In the other way, when you write a Bash shell script, a modification is necessary for it to run on a Bourne shell.

From Bash to Bourne Shell

Bourne is available without the need to install. How to switch from Bash to Bourne? You just have to open a terminal window. Then some steps will come. First, start with the chsh command and type in your user password. A prompt appears, type /bin/sh for your new shell. Then type su – USERNAME and finally type your user password again.

If this was successful, your new shell is USER@HOSTNAME: ~§ – where USER is your user name, HOSTNAME the name of your computer.

To get the real Shell Bourne version, you will have to use FreeBSD or Unix.

Sources & credits
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