10 Essential Shell Scripts You Need Today!

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Shell scripting offers a powerful way to automate repetitive tasks, streamline workflows, and maximize productivity. This article delves into ten remarkable shell scripts that can instantly enhance your efficiency and reduce manual efforts.

Understanding Shell Scripts

A shell script is essentially a text file containing a series of commands executed sequentially by the shell. Commonly utilized in Unix-based systems like Linux and macOS, these scripts can also be adapted for Windows environments using tools like Cygwin. By leveraging utilities such as bash, zsh, or sh, shell scripts can automate various tasks including file manipulation, system monitoring, and process control.

1. Automating Backup Tasks

Automated backups are essential for data security. A shell script can compress directories into archives and store them safely.

Steps:

1. Write a script that specifies the directory you want to back up.

2. Use tar to create a compressed archive.

3. Schedule the script to run daily using cron.

Script Example:

#!/bin/bash
tar -czvf /backup/myproject_$(date +%F).tar.gz /home/user/myproject/

• This command creates a compressed archive of the myproject directory with the current date in the filename.

Cron Job Scheduling:

0 2 * * * /path/to/backup_script.sh

This setup runs the backup script daily at 2 AM.

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2. Batch Renaming Files

Renaming files individually can be tedious. Automate this process with a simple loop.

Steps:

1. Write a script to loop through all files in a directory.

2. Rename each file according to a predefined pattern.

Script Example:

#!/bin/bash
for file in *.txt; do
    mv "$file" "newname_$file"
done

3. Disk Usage Monitoring

Prevent disk space issues by monitoring usage levels and sending alerts when necessary.

Steps:

1. Use df to check the disk usage.

2. Send an email if usage exceeds 80%.

Script Example:

#!/bin/bash
DISK=$(df / | grep / | awk '{ print $5 }' | sed 's/%//g')
if [ $DISK -gt 80 ]; then
    echo "Disk space critical: $DISK%" | mail -s "Disk Space Alert" [email protected]
fi

• This script sends an alert if disk usage exceeds 80%.

4. System Updates Automation

Keep your system secure by automating updates.

Steps:

1. Write a script that runs apt-get (or the package manager of your choice).

2. Automate the process with a cron job.

Script Example:

#!/bin/bash
sudo apt-get update && sudo apt-get upgrade -y

• This script updates the package list and installs any available updates.

Cron Job Scheduling:

0 4 * * 0 /path/to/update_script.sh

This runs the update script every Sunday at 4 AM.

5. Process Monitoring Script

Ensure critical services are running smoothly by monitoring processes.

Steps:

1. Use ps to check if the process is running.

2. Restart the process if it's not found.

Script Example:

#!/bin/bash
if ! pgrep -x "apache2" > /dev/null; then
    sudo systemctl restart apache2
fi

• This script checks if the Apache web server is running and restarts it if it's down.

6. Log Rotation Script

Manage disk space by automating log rotation.

Steps:

1. Identify the log files to rotate.

2. Compress old logs and delete the oldest ones.

Script Example:

#!/bin/bash
logrotate /etc/logrotate.d/apache2

• Use the logrotate utility to rotate logs for Apache, or customize it for other applications.

7. Network Performance Check Script

Diagnose connectivity issues by logging network performance metrics.

Steps:

1. Use ping to measure network latency.

2. Log the results for analysis.

Script Example:

#!/bin/bash
ping -c 5 google.com | grep 'time=' >> network_log.txt

8. Bulk File Compression Script

Compress multiple files in one go to save time.

Steps:

1. Use gzip or tar to compress all files in a directory.

2. Loop through the files to compress them.

Script Example:

#!/bin/bash
for file in *.log; do
    gzip "$file"
done

• This script compresses all .log files in the current directory.

9. Automated Email Notification Script

Set up email alerts based on system events.

Steps:

1. Trigger an email based on predefined conditions.

2. Use mail to send the email.

Script Example:

#!/bin/bash
echo "System alert" | mail -s "Alert: Service down" [email protected]

• This script sends an email notification when certain conditions are met.

10. Reboot Reminder Script

Notify users when a reboot is required after updates.

Steps:

1. Check if a reboot is required.

2. Send a reminder to the user.

Script Example:

#!/bin/bash
if [ -f /var/run/reboot-required ]; then
    echo "Reboot required" | wall
fi

• This script notifies all logged-in users that a reboot is required.

Conclusion

Shell scripts are invaluable tools for automating tasks, managing resources, and ensuring smooth system operations. By implementing these ten scripts, you can significantly increase your efficiency and focus on more critical tasks in your role as an IT professional or developer. Whether you're managing backups or monitoring system performance, mastering shell scripting offers long-term benefits that enhance productivity across various domains in tech.