What is bourne shell in linux

Unix / Linux — What is Shells?

A Shell provides you with an interface to the Unix system. It gathers input from you and executes programs based on that input. When a program finishes executing, it displays that program’s output.

Shell is an environment in which we can run our commands, programs, and shell scripts. There are different flavors of a shell, just as there are different flavors of operating systems. Each flavor of shell has its own set of recognized commands and functions.

Shell Prompt

The prompt, $, which is called the command prompt, is issued by the shell. While the prompt is displayed, you can type a command.

Shell reads your input after you press Enter. It determines the command you want executed by looking at the first word of your input. A word is an unbroken set of characters. Spaces and tabs separate words.

Following is a simple example of the date command, which displays the current date and time −

$date Thu Jun 25 08:30:19 MST 2009

You can customize your command prompt using the environment variable PS1 explained in the Environment tutorial.

Shell Types

In Unix, there are two major types of shells −

• Bourne shell − If you are using a Bourne-type shell, the $ character is the default prompt.
• C shell − If you are using a C-type shell, the % character is the default prompt.

The Bourne Shell has the following subcategories −

• Bourne shell (sh)
• Korn shell (ksh)
• Bourne Again shell (bash)
• POSIX shell (sh)

The different C-type shells follow −

The original Unix shell was written in the mid-1970s by Stephen R. Bourne while he was at the AT&T Bell Labs in New Jersey.

Bourne shell was the first shell to appear on Unix systems, thus it is referred to as «the shell».

Bourne shell is usually installed as /bin/sh on most versions of Unix. For this reason, it is the shell of choice for writing scripts that can be used on different versions of Unix.

In this chapter, we are going to cover most of the Shell concepts that are based on the Borne Shell.

Shell Scripts

The basic concept of a shell script is a list of commands, which are listed in the order of execution. A good shell script will have comments, preceded by # sign, describing the steps.

There are conditional tests, such as value A is greater than value B, loops allowing us to go through massive amounts of data, files to read and store data, and variables to read and store data, and the script may include functions.

We are going to write many scripts in the next sections. It would be a simple text file in which we would put all our commands and several other required constructs that tell the shell environment what to do and when to do it.

Shell scripts and functions are both interpreted. This means they are not compiled.

Example Script

Assume we create a test.sh script. Note all the scripts would have the .sh extension. Before you add anything else to your script, you need to alert the system that a shell script is being started. This is done using the shebang construct. For example −

This tells the system that the commands that follow are to be executed by the Bourne shell. It’s called a shebang because the # symbol is called a hash, and the ! symbol is called a bang.

To create a script containing these commands, you put the shebang line first and then add the commands −

Shell Comments

You can put your comments in your script as follows −

#!/bin/bash # Author : Zara Ali # Copyright (c) Tutorialspoint.com # Script follows here: pwd ls

Save the above content and make the script executable −

The shell script is now ready to be executed −

Upon execution, you will receive the following result −

/home/amrood index.htm unix-basic_utilities.htm unix-directories.htm test.sh unix-communication.htm unix-environment.htm

Note − To execute a program available in the current directory, use ./program_name

Extended Shell Scripts

Shell scripts have several required constructs that tell the shell environment what to do and when to do it. Of course, most scripts are more complex than the above one.

The shell is, after all, a real programming language, complete with variables, control structures, and so forth. No matter how complicated a script gets, it is still just a list of commands executed sequentially.

The following script uses the read command which takes the input from the keyboard and assigns it as the value of the variable PERSON and finally prints it on STDOUT.

#!/bin/sh # Author : Zara Ali # Copyright (c) Tutorialspoint.com # Script follows here: echo "What is your name?" read PERSON echo "Hello, $PERSON"

Here is a sample run of the script −

$./test.sh What is your name? Zara Ali Hello, Zara Ali $

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Is Bash Bourne Shell?

Bash (Bourne Again Shell ) is the free version of the Bourne shell distributed with Linux and GNU operating systems. Bash is similar to the original, but has added features such as command line editing.

What does bash mean in terminal?

Bash is an acronym for Bourne Again Shell. A shell is a terminal application used to interface with an operating system through written commands. Bash is a popular default shell on Linux and macOS. Git Bash is a package that installs Bash, some common bash utilities, and Git on a Windows operating system.

What exactly is bash?

Bash is a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell. … Bash can also read and execute commands from a file, called a shell script.

Are shell and bash the same?

Bash (bash) is one of many available (yet the most commonly used) Unix shells. Bash stands for “Bourne Again SHell”,and is a replacement/improvement of the original Bourne shell (sh). Shell scripting is scripting in any shell, whereas Bash scripting is scripting specifically for Bash.

Is KSH a Linux shell?

KornShell ( ksh ) is a Unix shell which was developed by David Korn at Bell Labs in the early 1980s and announced at USENIX on July 14, 1983. … KornShell is backward-compatible with the Bourne shell and includes many features of the C shell, inspired by the requests of Bell Labs users.

What was the first version of Linux?

While still a student at the University of Helsinki, Torvalds started developing Linux to create a system similar to MINIX, a UNIX operating system. In 1991 he released version 0.02; Version 1.0 of the Linux kernel, the core of the operating system, was released in 1994.

What is Bourne shell in Linux?

The Bourne shell is the original UNIX shell (command execution program, often called a command interpreter) that was developed at AT&T. Named for its developer, Stephen Bourne, the Bourne shell is also known by its program name, sh. … Bash is similar to the original, but has added features such as command line editing.

Is bash a high level language?

The term scripting language is also used in a wider sense, namely, to refer to dynamic high-level programming languages in general; some are strictly interpreted languages, while others use a form of compilation. … Bash, an interpreted scripting language for use on Unix and Unix-like operating systems and environments.

Is shell script a language?

A shell script is a computer program designed to be run by the Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text.

Does Mac use bash?

By default, Mac uses either zsh (Z shell) or bash (Bourne-again Shell) as the shell or command-line interpreter. Your Mac’s default shell will depend on the iteration of macOS that you’re using.

What is in C shell?

The C shell is a command processor which is typically run in a text window, allowing the user to type and execute commands. The C shell can also read commands from a file, called a script. … On Debian and some derivatives (including Ubuntu), there are two different packages: csh and tcsh.

What is .sh file?

A shell script is a text file that contains a sequence of commands for a UNIX-based operating system. It is called a shell script because it combines a sequence of commands, that would otherwise have to be typed into the keyboard one at a time, into a single script.

Who is Linux owned by?

The Linux trademark is owned by Linus Torvalds. Companies that use the term “Linux” for commercial distributions are apparently supposed to pay him a yearly licensing fee between $200 and $5000 for use of the name but there’s some dissension as to whether or not they actually pony up.

Who invented Linux OS?

Linus Torvalds, creator of the Linux Operating System, was born December 28, 1969 in Helsinki, Finland. His grandfather had a Commodore VIC-20 that he had the opportunity to work with; by age ten he was already dabbling in programming.

Why does Linux exist?

Linux was originally developed for personal computers based on the Intel x86 architecture, but has since been ported to more platforms than any other operating system. Because of the dominance of the Linux-based Android on smartphones, Linux also has the largest installed base of all general-purpose operating systems.

Is ksh a language?

KSH or ksh may refer to: Kenyan shilling, the currency of Kenya. KornShell, a Unix shell developed by David Korn in the early 1980s. Kölsch language (ISO 639-3 language code), a Ripuarian dialect spoken in Germany.

What is CSH in Linux?

The C shell is an interactive command interpreter and a command programming language that uses syntax similar to the C programming language. The shell carries out commands either interactively from a terminal keyboard or from a file. The csh command invokes the C shell.

Who wrote Korn shell?

David G. Korn (August 28, 1943) is an American UNIX programmer and the author of the Korn shell (ksh), a command line interface/programming language.

What is a shell in an operating system?

The shell is the outermost layer of the operating system. … A shell script is a sequence of shell and operating system commands that is stored in a file. When you log in to the system, the system locates the name of a shell program to execute. After it is executed, the shell displays a command prompt.

Which type is the wc command?

wc (short for word count) is a command in Unix, Plan 9, Inferno, and Unix-like operating systems. The program reads either standard input or a list of computer files and generates one or more of the following statistics: newline count, word count, and byte count.

What Posix means?

The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems.

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