Understand Linux Shell and Basic Shell Scripting Tips – Part I

The Linux shell, or command-line interface, is a powerful program that enables users to interact with the operating system via text-based commands.

Understanding the basics of the Linux shell and shell scripting can greatly enhance your efficiency and control over your system.

In this guide, we’ll explore key concepts and provide tips for both beginners and those looking to delve into basic shell scripting.

Understanding Linux Shell

The shell is a command-line program that interprets user commands and translates them into actions that the operating system can perform. It acts as an intermediary between the user and the Linux kernel, enabling users to control and manipulate the system through commands.

  • Shell – A command-line interpreter that connects a user to the operating system, allowing the execution of commands or the creation of text scripts.
  • Process – Any task that a user runs in the system is called a process. A process is a bit more complex than just a task.
  • File – A file resides on the hard disk (HDD) and contains data owned by a user.
  • X-Windows (X11) – A mode of Linux where the screen (monitor) can be split into small “parts” called windows, allowing a user to perform several tasks simultaneously, switch from one task to another easily, and view graphics in a visually appealing way.
  • Terminal – A monitor that has only the capability of displaying text, without graphics or with very basic graphics.
  • Session – The time between logging on and logging out of the system.

Types of Linux Shells

Linux supports several types of shells, with Bash (Bourne Again Shell) being the most prevalent. Other notable shells include Zsh (Z Shell), Fish, and Dash.

Each shell has its features and syntax, catering to different user preferences and needs.

  • Bash – It is the default shell for most Linux distributions and is widely used due to its versatility and powerful scripting capabilities.
  • Zsh – It is known for its enhanced features and improved user interface. It incorporates features from other shells, including Bash and Korn.
  • Fish – It is designed to be user-friendly with a focus on simplicity and discoverability by providing syntax highlighting and auto-suggestions for commands.
  • Dash – It is a lightweight shell designed for efficiency that is often used as the default system shell on minimalistic Linux distributions.
  • Ksh – It is a powerful shell with a focus on both interactive use and scripting that incorporates features from the Bourne shell (sh) and the C shell (csh).
  • Csh – It is designed with a syntax resembling the C programming language, which is known for its interactive features and scripting capabilities.

Basic Commands

There are thousands of commands for command-line users. How about remembering all of them? Hmm! Simply, you cannot. The real power of a computer is to simplify your work. To ease your work, you need to automate processes, and hence, you need scripts.

Scripts are collections of commands stored in a file. The shell can read this file and act on the commands as if they were typed at the keyboard. The shell also provides a variety of useful programming features to make scripts truly powerful.

Basics of Shell Programming

Shell programming involves creating scripts that utilize the capabilities of a shell, such as Bash, to automate tasks and execute commands. Understanding the basics of shell programming is essential for efficient and customized usage of the command-line interface.

Shebang (#!) Line

Every shell script begins with a shebang line specifying the interpreter to execute the script.

For Bash scripts, it is commonly #!/bin/bash.



Use # to add comments to your script. Comments are for human readability and are ignored by the shell.

# This is a comment


Variables store data in a script. Use the assignment operator (=) without spaces to assign values to variables.

greeting="Hello, Shell!"

User Input

Use the read command to obtain user input during script execution.

read -p "Enter your name: " username


The echo command is used to print output to the terminal, which is often used for displaying messages or variable values.

echo "Welcome, $username!"

Conditional Statements

Use if, elif, and else for decision-making in scripts.

if [ condition ]; then
  # code to execute if the condition is true
  # code to execute if the condition is false


Use for and while loops for repetitive execution of commands.

for i in {1..5}; do
  # code to repeat five times


Encapsulate code into functions for modularity and reusability.

function greet {
  echo "Hello, $1!"
greet "John"

Exit Status

Commands return an exit status. Use $? to check if the last command was successful (exit status 0) or encountered an error.

if [ $? -eq 0 ]; then
  echo "Command executed successfully."
  echo "Error during command execution."

File Permissions

When dealing with sensitive operations in scripts, use the chmod command to set appropriate permissions on the file.

chmod +x myscript.sh

About Shell Script

A shell script is simply a text file with a ".sh" extension that has executable permissions.

Here are some tips to guide you through the process of writing and executing a script:

  • Begin your script with a shebang line (#!/bin/bash) to specify the interpreter.
  • Add comments to explain the purpose of your script, especially for complex or lengthy code segments.
  • Use the echo command to print the “Hello, World!” message to the terminal.
  • Before execution, ensure your script has the necessary permissions using the chmod command, e.g., chmod +x script.sh.

“This is how your first shell script looks.”

# My first script

echo "Hello World!"

Save the above lines on a text file, make it executable, and run it, as described above.

Hello World Shell Script
Hello World Shell Script

Writing Second Script

Alright, it’s time to move on to the next script, which will display your ‘username‘ and list the currently running processes.

#! /bin/bash
echo "Hello $USER"
echo "Hey i am" $USER "and will be telling you about the current processes"
echo "Running processes List"
List Running Processes
List Running Processes

Was this cool? Writing a script is as simple as conceiving an idea and composing a sequence of commands. However, there are some limitations. Shell scripts excel at concise filesystem operations and scripting the integration of existing functionality through filters and command-line tools via pipes.

When your requirements extend beyond, be it in functionality, robustness, performance, efficiency, etc., then transitioning to a more full-featured language is advisable.

If you are already familiar with C/Perl/Python or any other programming language, acquiring proficiency in a scripting language shouldn’t be too challenging.

Writing Third Script

Moving on, let’s write our third and final script for this article. This script functions as an interactive script. Why not try executing this simple yet interactive script yourself and share your experience with us?

#! /bin/bash
echo "Hey what's Your First Name?";
read a;
echo "welcome Mr./Mrs. $a, would you like to tell us, Your Last Name";
read b;
echo "Thanks Mr./Mrs. $a $b for telling us your name";
echo "*******************"
echo "Mr./Mrs. $b, it's time to say you good bye"
Interactive Script
Interactive Script

Well, this is not the end. We tried to introduce you to the basics of scripting. In our future articles, we will delve deeper into the topic of scripting languages – a vast and ever-evolving field—to provide a more comprehensive understanding.

Your valuable thoughts in the comments are highly appreciated. Please like and share to help us reach a wider audience. Until then, relax, stay connected, and stay tuned.

Ravi Saive
I am an experienced GNU/Linux expert and a full-stack software developer with over a decade in the field of Linux and Open Source technologies

Each tutorial at TecMint is created by a team of experienced Linux system administrators so that it meets our high-quality standards.

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101 thoughts on “Understand Linux Shell and Basic Shell Scripting Tips – Part I”

  1. Thanks for this article. I am a beginner and your articles are helping me a lot. thanks for your good work.

    Please keep posting amazing articles like this.

  2. Hey I want to download Linux bible but its not download its show (“Thank you for your interest in Linux Bible– Complimentary Excerpt. We apologize that TradePub.com is no longer able to fulfill requests for this offer.”) I want this book any body send me this book on my email id please …..

    thank you
    abhishek kushwaha

    • @Abhishek,

      The books is no more available to download, as it is very old and not so useful now due to new changes in Linux, I suggest you to download other similar books.

    • @Narayan,

      If you see the second script closely you will see we used $USER variable, that means the current logged in user will display in the output of the script..

  3. Excellent. As a beginner, you ignited the taste and urge to learn more of Shell Scripting. Thanks for your great work.

  4. Hi,
    could you please help me with I want to know if there is any script or setting to lock computer after some idle time in the openLdap domain.

    Thank you

  5. This is very good for Starting Shell scrypting tutorial.
    Really i am very happy to use first time shell scrypting throught this site.

  6. Hello
    I have just started the RHEL7 training.I found lots of useful information from this website
    It helping me lot. Thanks for sharing knowledge.

    Satish Borkar

  7. I was confused about the first script that you have in this post why you have to read the variables as ‘a’ or ‘b’ and not ‘$a’ but when you output them you write the $ symbol next to them. I think there should be more explanation about this.

    Also, another thing that I noticed is that in the first script: you have this:
    echo “Hello $USER”
    echo “Hey i am” $USER “and will be telling you about the current processes”

    why in the first echo you surround $USER with double quotes and not in the second echo?

    Why in the third script you have lines ending with ; and some of them that don’t like:

    echo “Thanks Mr./Mrs. $a $b for telling us your name”;
    echo “*******************”

    Thank you

    Great website and great tutorial by the way.

    • @victor1
      The first variable is stored in a and the later in b,
      we can use the variable the way we want.

      read a will wait for the user to get input and will store in the variable a. Similar is the condition with variable b, in the above post.

  8. Excellent tutorial for beginners like me, Avishek. I’m a new Linux user, and I’d like to get started with the terminal commands as soon as I can. This is a good start, I guess. Very well explained. Thanks mate :)

  9. Hello thanks for sharing this amazing article. Please, I am having some problem with the third script. when I run the the script, only the first echo statement “what’s your first name” came out. the rest did not show and the shell prompt hang that I had to “cltr c” to bring it back.
    I copied and past the above code and give the script executable bit and still having the same issue. please help.
    Thanks again

    • copy and paste the below code as it is, to a file

      #! /bin/bash
      echo “Hey what’s Your First Name?”;
      read a;
      echo “welcome Mr./Mrs. $a, would you like to tell us, Your Last Name”;
      read b;
      echo “Thanks Mr./Mrs. $a $b for telling us your name”;
      echo “*******************”
      echo “Mr./Mrs. $b, it’s time to say you good bye”

      save it.
      Make it executable as chmod 755 script_name.
      Run as ./script_name

    • echo “Hey what’s Your First Name?”;
      read a;
      echo “welcome Mr./Mrs. $a, would you like to tell us, Your Last Name”;
      read b;

      When you type read a, it will show a prompt to accept input from you. the value you provided will be stored in a, if you entered xyjvfdj for a, a will have that value. Similar is the condition for Variable b.

  10. Thank you very much for this,
    i am using ubuntu 13.10 and it took me a while to find how to get started eventually i found vim editor and after that everything was smooth and quite enjoyable
    Thank you again

  11. i’ve 2 questions.please try to answer:—–

    1. what r enviroment variables and shell variables ?
    2. what is name of log file for filesystem check and errors?

  12. Avishek , Thanks once again. Would I need to create variables at the beginning of script. to have user indicate gender vs. and the echo Mr./Mrs. ?

    • You can create variable at the beginning, as it is an interactive script, if you finds it difficult, you can leave a comment here.

  13. Found your short lesson very helpful. I started thinking right after successfully running the script, and began to wonder if I could create two variables for Mrs and Mr. so that user can specify gender and use that input before name.

  14. Nice post. I am new-bee in linux and found of shell script. Your blog empowering my learning. Thanks for sharing your knowledge. Looking forward more quality post….

  15. Hi Avishek,

    I was going good with the first 2 script but the 3rd gives me headache.
    When I am executing the script, it gives me eror message:

    ./name.sh: line 8: s: command not found
    Hey whats time to say goodbey

    Do you know what causes the fault?

    “I have a MacbookPro”

    • @ kisszso, the script is perfectly ok. You need to copy and paste the above code, and nothing else, save it as anything.sh and run it as ./script_name.sh

      well “time to say goodbey” is a echo statement and will be printed on standard output as it is

    • Sure @ Lalit, we have already published a series of articles and will continue to produce such high quality articles, in future.

  16. Hi, keep them articles coming!
    Question: is the semicolon optional at the end of each line? Is there a rule when you have to put a ; or when you can omit it?

    • ; (semicolon) after a command forces the next command to wait till the previous command has finished.

      The best to learn is to experiment. Why don’t u remove the semicolon and run the script, this way u’ll learn something you will really proud of

      • At the end of a line a semicolon does nothing; it can be omitted.

        In the middle of a line it separates commands.


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