On CentOS/RHEL, you can use the systemctl command to check if a service is running or not. Example:   systemctl is-active <service-name>.service Replace <service-name> with the actual name of the service you want to check. The .service extension is necessary to specify that it is a system service. The systemctl is-active command returns “active” if … Read more

On macOS, you can use the wakeonlan command-line utility to send a Wake-on-LAN (WOL) magic packet to wake up a server. You’ll need to know the MAC address of the network interface that you want to wake up. You can typically find this information in the server’s documentation or by using a network scanner tool. … Read more

You can use the du command in a terminal to find the size of a directory in Linux. Example:   du -sh /path/to/directory The -s flag summarizes the directory size, and -h displays the output in a “human-readable” format (i.e., in GB or MB, instead of blocks). Replace /path/to/directory with the actual path to the … Read more

You can create a .tar.gz file in Linux using the tar command. The basic syntax is as follows: tar -czvf file_name.tar.gz directory_to_compress Here’s what each option does: c: Create a new archive. z: Compress the archive using gzip. v: Display verbose output, showing the progress of the compression process. f: Specify the filename of the … Read more

You can use the lsof command to find out which ports are open on a Linux system: lsof -i This will display a list of all open Internet sockets and the processes that have opened them. The -i option is used to specify that you only want to display information about Internet sockets. You can … Read more

You can find out the wireless connection speed rate on Mac OS X by using the following steps: Click on the Wi-Fi icon in the menu bar and select “Open Network Preferences.” In the Network Preferences window, select the Wi-Fi connection that you’re currently using. Click on the “Advanced” button. In the Advanced window, you’ll … Read more

When working with floating-point numbers in awk, unexpected results may occur due to the limitations of floating-point arithmetic. Floating-point numbers are stored in a binary format, which can cause inaccuracies in arithmetic operations, especially when adding or subtracting large or small numbers. Here are some tips to avoid unexpected results when working with floating-point numbers … Read more

To redirect mobile/smartphone traffic to the mobile version of a website using Nginx, you can use the if directive in your Nginx configuration file. Here’s an example configuration that redirects all mobile devices to a separate URL: server { listen 80; server_name example.com; root /var/www/example.com; if ($http_user_agent ~* ‘(iPhone|iPod|blackberry|android.*mobile|windows.*phone)’) { return 302 http://m.example.com$request_uri; } # … Read more

To log everyone out of the system, you can use the kill command. To log out all users except yourself, you can use the following command: kill -HUP -1 To log out all users including yourself, you can use the following command: kill -HUP 1 Note that using this command will terminate all processes running … Read more

In the csh shell, you can use a loop to perform a set of commands multiple times. Here are a few examples of loops in csh: For loop: #!/bin/csh set i = 1 while ( $i <= 10 ) echo “Iteration $i” @ i++ end This script will print “Iteration 1” to “Iteration 10”. For … Read more