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What Is Shell?
A Shell is a command-line interface to the Unix operating system. It collects data from you and runs code blocks on that data. The output of a code is displayed once it has completed its execution. Shell is a command-line interface that allows us to run commands, programs, and shell scripts. Shells come in a variety of flavours, much as operating systems come in a variety of flavours.
A shell can be launched using the shell command in the command-line interface (CLI) on Linux-based operating systems, allowing users to direct operations using computer commands, text, or Linux script. Programming languages have their own shells, which provide them independence from the operating system and allow cross-platform interoperability.
Why and where Linux shell script Is used?
- Your task will be less monotonous with the shell. You can automate repetitive and tedious activities with the shell, freeing up your time to accomplish more fascinating things.
- Your work will be less prone to errors, thanks to the shell. When people repeat the same action a hundred times (or even ten times), they are more likely to make mistakes. Your computer can repeat the process thousand times without making any mistakes.
- The shell programming improves the consistency of your work. When you work with the command line (rather than a GUI), your computer retains track of every step you take, which you may refer to if you need to redo something. It also allows you to convey what you've done so that others can examine or apply your method to new data.
- Many corporate tasks demand a significant amount of processing power and cannot be completed on your own computer. Remote computers or cloud computing, which can only be accessed through a shell, are ideal for these jobs.
Shells are usually interactive, which means they accept user commands as input and execute them. However, there are occasions when we need to run a series of commands on a regular basis, in which case we must type all commands into the terminal each time.
We can write these commands in a file and execute them in the Linux shell script to prevent this repetitive labour because a shell can take commands as inputs from a file. Shell Scripts or Shell Programs are the names given to these files. The batch file in MS-DOS is analogous to shell scripts, and the .sh file extension is used to save shell scripts.
Shell scripts have the same syntax as other programming languages. Getting started will be quite simple if you have prior knowledge of any programming language such as Python, C/C++, or others.
Shell scripts have the following components
- Keywords – if, else, break etc.
- Commands – cd, ls, echo, pwd, touch etc.
- Control flow – if..then..else, case and shell loops etc.
The shell issues the prompt, $, sometimes known as the command prompt. You can enter a command whilst the prompt is shown.
After you press Enter, Shell reads your input. It looks at the first word of your input to decide which command you wish to run. A word is a continuous string of characters that are separated by spaces and tabs.
Extended Shell Scripts
Shell scripts must include certain mandatory and extended structures that instruct the shell environment what to do and when. Most scripts, however, are more complicated than the one above.
After all, the shell is a full-fledged programming language with variables, control structures, and so on. A script is still just a series of commands executed in order, no matter how complex it becomes.
A kernel is computer software that is at the heart of a computer's operating system, controlling everything in it. It is in charge of the Linux system's following resources:
Terminals, usually referred to as command lines or consoles, allow us to complete and automate activities on a computer without using a graphical user interface. It has a user interface that allows users to type instructions and output content.
We can use a computer terminal to send simple text instructions to our computer to accomplish things like traverse through a directory or copy a file, and it's the foundation for a lot of more advanced automation and programming skills.
We now know what is shell, and how to use the shell to perform various functions on our system. This gives us an advantage over using a GUI to interface with the file system since it allows us to operate on a remote server, perform the same set of operations on a huge number of files fast, etc.
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