Shell Scripting Tutorial

By Muhammad Waleed Akram

Introduction

Shell scripting is the art of telling efficiently your operating system (OS) exactly what to do. This tutorial aims to take you from basic shell scripting to a level where you can comfortably automate complex tasks and work like a real system engineer.

What Exactly is a Shell?

A shell is an interface between you and the kernel. It takes commands you type and executes them on your behalf.

Some popular shells are:

Bash (Bourne Again Shell)
Zsh
Fish

Shell scripting is simply writing multiple shell commands into a file so that they can run sequentially.

1. Setting Up

Ensure you have access to a shell environment:

Linux/macOS: Open the Terminal
Windows: Use Git Bash or WSL (Windows Subsystem for Linux). I am using Ubuntu because RISC-V tools work well with it.

echo $SHELL

2. Your First Script

Create a file named myscript.sh:

vim myscript.sh

Then type:

#!/bin/bash
echo "Hello, Shell World!"

Save and exit with :wq.

Understanding the Script Line-by-Line

#!/bin/bash: Shebang to define interpreter
echo: Used to print output

3. Working with Files and Directories

mkdir new_project
cd new_project
ls
touch file{1..5}.txt
rm file1.txt
rmdir new_project

4. Command-Line Power: Pipes and Redirection

ls | grep "project"
echo "Backup complete" > backup.log
cat backup.log

5. File Manipulation

cat filename.txt
head -n 2 filename.txt
tail -n 3 filename.txt
cp source.txt destination.txt
mv oldname.txt newname.txt
mv file.txt /path/to/directory/

6. Working with Text Files

grep "computing" file1.txt
cut -c5-10 file1.txt
paste file1.txt backup.log

7. Variables and Substitution

name="Waleed"
echo "Hello, $name!"

8. Input and Output

read -p "Enter your city: " city
echo "You live in $city"
echo "This is a log entry" >> logfile.txt

9. Control Structures

read -p "Enter a number: " num
if [ $num -gt 0 ]; then
    echo "Positive number"
elif [ $num -lt 0 ]; then
    echo "Negative number"
else
    echo "Zero"
fi

10. Bash Comparison Operators Cheat Sheet

Operator	Meaning
-gt	Greater Than
-lt	Less Than
-ge	Greater Than or Equal
-le	Less Than or Equal
-eq	Equal (numbers)
-ne	Not Equal (numbers)
==	Equal (strings)
!=	Not Equal (strings)
-z	Empty string
-n	Non-empty string
-w	Writable
-x	Executable
-r	Readable
-d	Directory

10. Loops

For Loop:

for i in {1..5}; do
    echo "Number: $i"
done

for file in *.txt; do
    echo "Found file: $file"
    wc -l "$file"
done

for (( i=0; i<=5; i++ )); do
    power=$(( 2**i ))
    echo "2^$i = $power"
done

While Loop:

count=1
while [ $count -le 5 ]
do
    echo "Count: $count"
    ((count++))
done

11. Functions

greet() {
    echo "Welcome, $1!"
}
greet "Waleed"

12. Conclusion

This tutorial provides a complete beginner-friendly journey into shell scripting, covering everything from basic commands to functions and loops. Along the way, I included my own screenshots to make the concepts even easier to understand and to support students in practical learning. With consistent practice, you will be able to automate tasks and work confidently like a real system engineer. Keep exploring and scripting, your Linux journey has just begun!