Bash Tutorial

Bash Logo

Bash (Bourne Again SHell) is a widely used Unix shell and command language. It is the default shell on most Linux distributions and macOS, and is popular for scripting, automation, and system administration.

How to Install Bash

Bash is pre-installed on most Linux and macOS systems. To check your version:

$ bash --version

To install or update Bash on Ubuntu:

$ sudo apt update
$ sudo apt install bash

How to Use Bash

1. Running Bash

Open a terminal and type commands directly, or write them in a script file (e.g., myscript.sh).

To run a script:

$ bash myscript.sh

Or make it executable:

$ chmod +x myscript.sh
$ ./myscript.sh

2. Basic Commands

ls — List files and directories
cd — Change directory
pwd — Print working directory
echo — Print text
cat — Display file contents
cp — Copy files
mv — Move/rename files
rm — Remove files

Example:

ls -l
cd /home/user
pwd
echo "Hello, World!"

3. Variables

Assign a value to a variable (no spaces around =):

name="Alice"
echo $name

4. Conditionals

if [ "$name" = "Alice" ]; then
  echo "Hello, Alice!"
else
  echo "You are not Alice."
fi

5. Loops

For Loop:

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

While Loop:

count=1
while [ $count -le 3 ]; do
  echo $count
  count=$((count + 1))
done

6. Functions

say_hello() {
  echo "Hello, $1!"
}
say_hello "Bob"

7. Script Example

Create a file called greet.sh:

#!/bin/bash
name=$1
echo "Hello, $name!"

Make it executable and run:

$ chmod +x greet.sh
$ ./greet.sh Alice

8. Cleaning Up

To clear the terminal screen:

$ clear

9. Advantages of Bash

Ubiquity: Available on most Unix-like systems.
Simplicity: Easy to learn and use for automation.
Powerful scripting: Supports variables, conditionals, loops, and functions.
Integration: Works well with other command-line tools.

10. Further Resources

Summary

Bash is a powerful and flexible shell for command-line users and script writers. Its simplicity and ubiquity make it a great tool for beginners and experts alike.