Linux Shell and Shell Scripts: Basics and Key Concepts

All the Linux distributions have a shell, and users interact with it through the terminal. In the article, we will talk about Linux shell and shell scripts, so you will have a better understanding of the tech terminology and some details about Linux functioning.

Understanding the Kernel

The kernel is the center of the Linux OS that has full control over all the resources. We are specifically talking about:

• ​Process management
• ​File management
• ​Device management
• ​Memory management
• ​I/O management

There is a huge misunderstanding that Linus Torvalds created the Linux OS, but in fact, he developed the Linux kernel.

Exploring the Shell

Shell is a user program with the help of which clients can have access to the system services. Shell functions on the readable commands that are sent and converted so that the kernel can understand them. It works like an interpreter that helps to understand commands received from the input devices. Communication through the shell begins when a client enters the terminal.

The shell can be divided into the following categories:

• Graphic shell
• Command line shell

Command Line Interface (CLI) Shell

Users can access the shell via the command line interface. In Linux, it is called Terminal, and the readable commands are executed through it. After the execution, it is possible to see the result – whether the process was successfully completed or not.

Users with no or minimal tech skills might find this process a little bit challenging because they need to have a basic understanding of commands. With a little practice, the process becomes intuitive with time. This is an extremely powerful approach because lots of commands can be executed together, and some processes might be easily automated.

Graphical User Interface (GUI) Shells

GUI shell offers access to a more manipulative interface where users can move, open, close, and resize windows. This is available in the Ubuntu OS, so users can interact with programs differently. There are no commands as in a command line interface, and that’s why it is considered to be a more user-friendly variant.

On the Linux system, there are several shells, such as:

• ​KSH.
• ​CSH.
• ​BASH. This is the more popular variant that is available on most Linux systems.

All the shells are somehow similar, but they might differ in the functions and usage of various commands.

Defining the Terminal

Terminal is an interface through which users can interact with the shell. So, it is possible to enter the needed command and immediately see the results on the screen. Also, a terminal is used for the execution of huge automated tasks. To find the terminal, you just need to find the search box.

Introduction to Shell Scripting

Most of the commands get immediate output after typing, but there are also cases when you need to use a bunch of commands to achieve certain results.

To exclude the necessity to type all the bunch of commands again and again, it is possible to save them in files and execute whenever it is needed. Such a process is called shell scripting, each such file is saved with the ‘.sh’ extension.

Shell script has also got some syntax, and if you have some experience with programming languages, that might be helpful for its understanding. The scripts usually include the following elements:

• ​Functions
• ​Commands
• ​Keywords
• ​Control flow

Importance of Shell Scripts

Here are some explanations why a shell script is a necessity:

• Monitoring of the system.
• ​To minimize repetitive workload.
• ​Adding new functionality.
• ​Routine backups.

Key Benefits of Shell Scripting

• ​Quick start
• ​Quick writing of shell scripts
• ​Interactive debugging.
• ​Syntax and commands are the same as in the command line.

Limitations of Shell Scripting

• ​Execution speed can be slower
• ​One mistake can totally change the command, and that can be harmful
• ​Not appropriate for the complex tasks
• ​Some flaws in the language syntax
• ​Offer a minimal data structure

Basic Shell Scripting Example Using Bash

#!/bin/bash
# A simple bash script to jump up the directory tree to a specified folder name
jump() {
​local target="$1"
​local dir="$PWD"
​# Loop until we reach the root directory
​while [[ "$dir" != "/" ]]; do
    ​if [[ "$(basename "$dir")" == "$target" ]]; then
        ​cd "$dir" || return
        ​return
    ​fi
    ​dir=$(dirname "$dir")
​done
​echo "Directory '$target' not found in the current path."
}

Final Thoughts

Now, you have a better understanding of the Linux systems, their major parts such as kernel, shell, and also the way everything is interacting. With the help of shell scripting, users can automate lots of processes and simplify task completion.