Linked lists are a fundamental data structure that every software developer should understand. They form the basis for many other data structures and algorithms. In this blog post, we’ll explore how to implement a linked list in Java and cover some of the trickiest parts that you might encounter during interviews. What is a Linked List? A linked list is a linear data structure where each element, called a node, contains a reference (or link) to the next node in the sequence. Unlike arrays, linked lists do not require contiguous memory allocation, making them more flexible for dynamic data structures. ...

The essential commands for creating, modifying, and deleting user accounts, as well as managing user privileges and groups. User Management: Creating a new user: sudo useradd username Set the user’s home directory and shell: sudo useradd -d /home/username -s /bin/bash username Setting a password for the user: sudo passwd username Deleting a user: sudo userdel -r username Modifying user properties: sudo usermod -g newgroup -aG group1,group2 -d /new/home/directory -s /bin/newshell username Listing all users: ...

GitHub CLI, or gh, is a powerful tool that brings the full functionality of GitHub to your command line. Whether you’re managing repositories, creating issues, or reviewing pull requests, gh streamlines your workflow by enabling you to interact with GitHub directly from your terminal. In this guide, we’ll walk through the installation process on Ubuntu and provide a cheat sheet of commonly used commands. Installation on Ubuntu Using APT (Advanced Package Tool) Open your terminal and follow these steps: ...

Developers often work on projects that require specific programming languages and versions. Managing these different environments can be challenging, but with the right tools, you can streamline the process and improve your workflow. In this blog post, we’ll walk you through setting up four important version management tools: nvm, pyenv with virtualenv, jenv, and Rust on an Ubuntu system. Table of Contents Introduction Installing nvm (Node Version Manager) Setting Up pyenv with virtualenv (Python Version Manager) Configuring jenv (Java Environment Manager) Managing Rust Versions with Rustup Conclusion Introduction Setting up a development environment involves managing different versions of programming languages to ensure compatibility with various projects. The tools we’ll cover in this guide provide an organized approach to this process, making it easier to switch between different language versions. ...

Bash script to export all data from a MySQL/MariaDB database to CSV files: #!/bin/bash DB_USER="your_username" DB_PASS="your_password" DB_NAME="your_database" TABLES=$(mysql -u$DB_USER -p$DB_PASS -e "USE $DB_NAME; SHOW TABLES;" | grep -v "Tables_in") for TABLE in $TABLES; do mysql -u$DB_USER -p$DB_PASS -e "USE $DB_NAME; SELECT * FROM $TABLE;" | sed 's/\t/","/g;s/^/"/;s/$/"/' > "$TABLE.csv" done echo "CSV export complete!" Replace your_username, your_password, and your_database with your actual database credentials and database name. Save the script to a file, make it executable with chmod +x scriptname.sh, and then run it using ./scriptname.sh in your terminal. This script will create a CSV file for each table in your database, containing all the data from that table. ...

Step 1: Update Your System: Begin by ensuring your Ubuntu system is up to date. In the terminal, execute the following commands: sudo apt update sudo apt upgrade Step 2: Installing OpenJDK: Ubuntu’s default repositories offer convenient access to OpenJDK packages. For this guide, we’ll focus on OpenJDK 11, an LTS version. Install it using the package manager: sudo apt install openjdk-11-jdk Step 3: Verify the Installation: Once installation is complete, verify that Java is successfully installed by checking the version: ...

Below is the Bash script to download and set up Nginx server with SSL using a self-signed certificate and user-provided details on RHEL (Red Hat Enterprise Linux): #!/bin/bash # Check if the script is running with root privileges if [ "$EUID" -ne 0 ]; then echo "Please run this script as root or with sudo." exit 1 fi # Check if a domain name is provided as an argument if [ $# -ne 1 ]; then echo "Usage: $0 <domain_name>" exit 1 fi # Assign the provided domain name to a variable domain_name="$1" # Prompt the user for SSL certificate details read -p "Enter the Country Code (e.g., US): " country_code read -p "Enter the State or Province (e.g., California): " state read -p "Enter the Locality or City (e.g., San Francisco): " city read -p "Enter the Organization Name (e.g., My Company): " organization # Update package lists yum update -y # Install Nginx yum install -y epel-release yum install -y nginx # Start Nginx service systemctl start nginx # Enable Nginx to start on boot systemctl enable nginx # Check if Nginx is running if systemctl is-active --quiet nginx; then echo "Nginx has been installed and is running." else echo "Failed to start Nginx. Check for any errors during installation." exit 1 fi # Generate self-signed SSL certificate with user-provided details mkdir -p /etc/nginx/ssl openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/nginx/ssl/nginx.key -out /etc/nginx/ssl/nginx.crt -subj "/C=${country_code}/ST=${state}/L=${city}/O=${organization}/CN=${domain_name}" # Configure Nginx to use SSL cat > /etc/nginx/conf.d/default.conf << EOF server { listen 80; listen [::]:80; server_name ${domain_name}; return 301 https://\$host\$request_uri; } server { listen 443 ssl; listen [::]:443 ssl; server_name ${domain_name}; ssl_certificate /etc/nginx/ssl/nginx.crt; ssl_certificate_key /etc/nginx/ssl/nginx.key; location / { root /usr/share/nginx/html; # Change this to the root directory of your website index index.html index.htm; } } EOF # Test Nginx configuration for syntax errors nginx -t # Reload Nginx to apply the changes systemctl reload nginx # Display the server IP address and open the default Nginx page in the browser server_ip=$(curl -s http://checkip.amazonaws.com) echo "Nginx with SSL is serving at https://${domain_name}/" # Optionally, you can open the default Nginx page in the default web browser # Uncomment the following line if you want to open the page automatically # xdg-open "https://${domain_name}/" Save the script to a file, for example, nginx_ssl_setup_rhel.sh. Make sure to give it executable permissions using the following command: ...

Below is a Bash script to download and set up Nginx server with SSL using a self-signed certificate and user-provided details: #!/bin/bash # Check if the script is running with root privileges if [ "$EUID" -ne 0 ]; then echo "Please run this script as root or with sudo." exit 1 fi # Check if a domain name is provided as an argument if [ $# -ne 1 ]; then echo "Usage: $0 <domain_name>" exit 1 fi # Assign the provided domain name to a variable domain_name="$1" # Prompt the user for SSL certificate details read -p "Enter the Country Code (e.g., US): " country_code read -p "Enter the State or Province (e.g., California): " state read -p "Enter the Locality or City (e.g., San Francisco): " city read -p "Enter the Organization Name (e.g., My Company): " organization # Update package lists apt-get update # Install Nginx apt-get install -y nginx # Start Nginx service systemctl start nginx # Enable Nginx to start on boot systemctl enable nginx # Check if Nginx is running if systemctl is-active --quiet nginx; then echo "Nginx has been installed and is running." else echo "Failed to start Nginx. Check for any errors during installation." exit 1 fi # Generate self-signed SSL certificate with user-provided details openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/nginx/ssl/nginx.key -out /etc/nginx/ssl/nginx.crt -subj "/C=${country_code}/ST=${state}/L=${city}/O=${organization}/CN=${domain_name}" # Configure Nginx to use SSL cat > /etc/nginx/sites-available/default << EOF server { listen 80; listen [::]:80; server_name ${domain_name}; return 301 https://\$host\$request_uri; } server { listen 443 ssl; listen [::]:443 ssl; server_name ${domain_name}; ssl_certificate /etc/nginx/ssl/nginx.crt; ssl_certificate_key /etc/nginx/ssl/nginx.key; location / { root /var/www/html; # Change this to the root directory of your website index index.html index.htm; } } EOF # Create a symbolic link to enable the configuration ln -s /etc/nginx/sites-available/default /etc/nginx/sites-enabled/ # Test Nginx configuration for syntax errors nginx -t # Reload Nginx to apply the changes systemctl reload nginx # Display the server IP address and open the default Nginx page in the browser server_ip=$(curl -s http://checkip.amazonaws.com) echo "Nginx with SSL is serving at https://${domain_name}/" # Optionally, you can open the default Nginx page in the default web browser # Uncomment the following line if you want to open the page automatically # xdg-open "https://${domain_name}/" Save the script to a file, for example, nginx_ssl_setup.sh. Make sure to give it executable permissions using the following command: ...

Setting up a Python virtual environment in Linux involves a few steps. Here’s a step-by-step guide: Open a terminal: Launch the terminal application on your Linux distribution. Install Python: Most Linux distributions come with Python pre-installed. However, if it’s not installed or you want a specific version, you can install it using your distribution’s package manager. For example, on Ubuntu or Debian-based systems, you can use the following command to install Python 3: ...