🐚 Shell Scripting Challenge: Directory Backup with Rotation .

📋 Challenge Description

The task is to write a bash script that:

1. Accepts a directory path as a command-line argument.

2. Creates a timestamped backup folder in the specified directory.

3. Copies all the files from the directory into this new backup folder.

4. Keeps only the last 3 backups and deletes any older ones automatically.

🛠 Shell Script: backup_with_rotation.sh

Here’s the script to handle the challenge step-by-step:

#!/bin/bash

# Check if a directory is provided as an argument
if [ -z "$1" ]; then
    echo "❌ Error: Please provide a directory path as an argument!"
    exit 1
fi

# Assign the directory path
DIR_PATH="$1"

# Check if the provided path exists and is a directory
if [ ! -d "$DIR_PATH" ]; then
    echo "❌ Error: The specified path does not exist or is not a directory!"
    exit 1
fi

# Generate a timestamp for the backup folder
TIMESTAMP=$(date +"%Y-%m-%d_%H-%M-%S")
BACKUP_FOLDER="backup_${TIMESTAMP}"

# Create the backup folder
mkdir "$DIR_PATH/$BACKUP_FOLDER"

# Copy all files from the specified directory to the backup folder
cp -r "$DIR_PATH"/* "$DIR_PATH/$BACKUP_FOLDER" 2>/dev/null
echo "✅ Backup created: $DIR_PATH/$BACKUP_FOLDER"

# Change to the directory containing the backups
cd "$DIR_PATH" || exit

# Get a list of backup folders matching the pattern "backup_*"
BACKUPS=(backup_*)
NUM_BACKUPS=${#BACKUPS[@]} # Count the number of backups

# If more than 3 backups exist, remove the oldest ones
if [ "$NUM_BACKUPS" -gt 3 ]; then
    DELETE_COUNT=$((NUM_BACKUPS - 3))
    for ((i = 0; i < DELETE_COUNT; i++)); do
        rm -rf "${BACKUPS[$i]}"
        echo "🗑 Removed old backup: ${BACKUPS[$i]}"
    done
fi

🧩 How the Script Works

Step-by-Step Breakdown:

1. Input Validation

   • The script checks if the directory path is provided as an argument.

   • It verifies that the given path exists and is a directory.

2. Create a Timestamped Backup

   • A unique backup folder is created using the current timestamp, e.g., backup_2025-02-12_12-30-45.

   • Files from the directory are copied into this backup folder.

3. Backup Rotation

   • The script lists all existing backup folders matching the pattern backup_*.

   • If there are more than 3 backups, the oldest backups are deleted to retain only the latest 3.

💻 Example Execution

Command:

$ ./backup_with_rotation.sh /home/user/documents

First Execution (2025-02-12):

Output:

✅ Backup created: /home/user/documents/backup_2025-02-12_10-15-30
✅ Backup created: /home/user/documents/backup_2025-02-12_11-45-00
✅ Backup created: /home/user/documents/backup_2025-02-12_12-30-45

Directory contents:

backup_2025-02-12_10-15-30  
backup_2025-02-12_11-45-00  
backup_2025-02-12_12-30-45  
file1.txt  
file2.txt  
...

Second Execution (2025-02-13):

Output:

✅ Backup created: /home/user/documents/backup_2025-02-13_08-00-00
🗑 Removed old backup: backup_2025-02-12_10-15-30

Directory contents (after rotation):

backup_2025-02-12_11-45-00  
backup_2025-02-12_12-30-45  
backup_2025-02-13_08-00-00  
file1.txt  
file2.txt  
...

🎯 Notice: The oldest backup (backup_2025-02-12_10-15-30) is deleted to retain only the last 3 backups.

🔍 Key Shell Commands Used

Here are the main commands powering the script:

1. date
   Generates a unique timestamp for each backup.

    date +"%Y-%m-%d_%H-%M-%S"
   

2. mkdir
   Creates a new directory for the backup folder.

    mkdir "$DIR_PATH/$BACKUP_FOLDER"
   

3. cp
   Copies all files from the source directory to the backup folder.

    cp -r "$DIR_PATH"/* "$DIR_PATH/$BACKUP_FOLDER"
   

4. rm
   Deletes the oldest backups to maintain only the last 3 backups.

    rm -rf "${BACKUPS[$i]}"
   

⏰ Scheduling Backups with Cron

Automate the script to run daily at 2:00 AM using the following cron command:

0 2 * * * /path/to/backup_with_rotation.sh /home/user/documents