6.1 Bash Scripting Basics

A script is just a text file with a list of commands.

The Shebang (#!)

The first line tells Linux which interpreter to use.

#!/bin/bash

First Script (Variables)

Create hello.sh:

#!/bin/bash

# Define a variable (No spaces in assignment!)
NAME="World"

# Print it using $
echo "Hello, $NAME"

Make it executable: chmod +x hello.sh. Run it: ./hello.sh.

Control Flow

If Statement

if [ -f "/etc/passwd" ]; then
    echo "Filesystem is sane."
else
    echo "Something is very wrong."
fi

For Loop

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

Exit Codes

Every command returns a status.

• 0: Success.
• Non-zero: Error. You check it with $?.