Atul Maurya - Blogs

1. What is the Bourne Shell (sh)?

Think of sh as the oldest grandfather of all shells in Linux/Unix.

It is very simple , stable , available on almost every Unix system

It is recommended for scripting because it works everywhere

So imagine a very old Nokia phone not fancy, but never fails. That’s sh.

It doesn’t have fancy features, no colours, no autosuggestions — just works.

2. Why do we still use sh today?

Because:

Every system understands sh

No matter whether you use Ubuntu, macOS, or a server from 1990 sh will run.

Perfect for scripts

Many system scripts start with:

#!/bin/sh

This tells the OS:

➡ “Run this script using the simple, standard shell.”

✔ Most portable

Other shells (bash, zsh, fish) have extra features.

But sh scripts run everywhere.

3. Where is sh located?

Most commonly→ /bin/sh.

This file points to the shell program.

4. How does sh behave?

sh is basic:

No auto-completion, coloured fancy prompts , shortcuts.

Very small set of features :

Command execution
Variable assignment
Command substitution
Input / output redirection
Pipes
Conditional statements (if, else)
Loops (for, while) etc.

It is mainly meant for running scripts, not for interactive use.

5. How to write your first sh script

Let’s write a very simple script:

hello.sh

#!/bin/sh
echo "Hello from sh"

Steps to run:

1️⃣ Make file executable

chmod +x hello.sh

2️⃣ Run it

./hello.sh

✔ Output:

Hello from sh

6. When should YOU use sh?

Use sh when:

✔ You're writing a script that should run on ANY machine

✔ You want maximum compatibility

✔ You don’t need advanced features like arrays, functions with names, etc.

Don’t use it for daily terminal usage bash/zsh is better for daily work.

To Keep in Mind:

Imagine sh is the grandfather of all shells — simple, slow, stable, and respected by every OS.

When you use #!/bin/sh, you’re basically saying:

👉 “Grandpa, handle this. You never fail.”

Home work (Must go though these Features) For getting a basic Idea :

What can sh do? (Basic commands you should know)

1. Print something

echo "My name is Atul"

2. Variables

name="Atul"
echo $name

3. Simple if

if [ $name = "Atul" ]; then
  echo "Yes, I am Atul"
fi

4. Simple loop

for i in 1 2 3; do
  echo $i
done

5. Running commands

ls
pwd
mkdir test

A. ) Bourne Shell (sh)