Example 1: Backup Script

• Create a script that automatically backs up files or directories.

#!/bin/bash

SOURCE_DIR="/home/user/documents"
BACKUP_DIR="/home/user/backups"

mkdir -p $BACKUP_DIR
cp -r $SOURCE_DIR/* $BACKUP_DIR

echo "Backup completed successfully!"

• This script creates a backup of the documents directory into the backups directory.
• It uses the cp command to copy files and directories (-r for recursive).
• It checks and creates the backup directory (mkdir -p).

Example 2: System Monitoring Script

• Create a script to monitor CPU and memory usage.

#!/bin/bash

echo "CPU Usage:"
top -n 1 | grep "Cpu(s)" | awk '{print $2 + $4 "% CPU used"}'

echo "Memory Usage:"
free -h | grep Mem | awk '{print $3 "/" $2 " used"}'

echo "Disk Space Usage:"
df -h | grep "^/dev/"

• top: To check CPU usage.
• free: To check memory usage.
• df: To check disk usage.

Example 3: Log Rotation Script

A log rotation script can help manage log files and prevent them from growing too large.

#!/bin/bash

LOG_DIR="/var/log/myapp"
MAX_SIZE=1048576  # 1MB in bytes

for log_file in $LOG_DIR/*.log; do
	  if [ $(stat -c %s "$log_file") -gt $MAX_SIZE ]; then
        mv "$log_file" "$log_file.old"
        echo "Archived $log_file"
    fi
done

• This script checks all .log files in the specified directory.
• If a log file exceeds the size limit, it is renamed (archived) by adding .old.

Automating Scripts with Cron Jobs

• You can schedule your scripts to run automatically using Cron Jobs.
• This is especially useful for recurring tasks like backups, system monitoring, and log rotation.