Create a Bash Script, Step by Step

What a Bash script is

A Bash script is a text file with commands that run one after another. Use scripts to automate jobs you repeat, such as backups and updates.

Step 1: Pick an editor

You can use any text editor. nano is easy for beginners and vim is more powerful. Install them if needed:

sudo apt install nano
sudo apt install vim

Step 2: Write the script

Create the file. The extension .sh is a habit and not a must:

nano bash_script.sh

The first line is the shebang. It tells the system which program runs the file:

#!/bin/bash

Add your commands below it:

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

Save and close the file.

Step 3: Make it executable

chmod +x bash_script.sh

Step 4: Run it

./bash_script.sh

You can also start it with bash and no execute right:

bash bash_script.sh

Step 5: Test and debug

Test the script on a copy of your data first. To see each command as it runs, start it in debug mode:

bash -x bash_script.sh

A full example

1. Create the file:

nano bash_script.sh

1. Write this:

#!/bin/bash
# Store a number in a variable
number=10
# Print the number
echo "The number is: $number"

1. Give execute rights to all users (use chmod +x if you only need yourself):

chmod a+x bash_script.sh

1. Run it with either command:

./bash_script.sh
bash bash_script.sh

Bash basics

• Comments start with #.
• Variables are set without spaces: name="Hostvento", and used with $name.
• Conditions: if [ "$a" -gt 5 ]; then ... fi
• Loops: for i in 1 2 3; do echo $i; done
• Input: read answer waits for the user.
• Exit codes: exit 0 means success.

Quick recap

• Start with #!/bin/bash.
• Make the file executable with chmod +x.
• Run it with ./script.sh, and debug with bash -x.