You can use the grep command in Linux to remove the lines from file A that appear in file B. The basic syntax is − grep -v -f fileB.txt fileA.txt > outputFile.txt This command uses the -v option to invert the match, so that it returns lines that do not match those in file B. The -f option specifies the file containing the patterns to match. The output is redirected to a new file called outputFile.txt. Alternatively, you can use sed command sed -i '/$(grep -f fileB.txt fileA.txt)/d' fileA.txt This command uses the -i option to edit the ... Read More

You can run multi-line shell code at once by using a shell script or by using a command line tool such as the bash or sh command to execute the code in a single prompt. To create a shell script, you can use a text editor to write the code and save it with a .sh file extension. For example, you can create a file called "script.sh" and add the following code − #!/bin/bash echo "Hello, World!" echo "This is a shell script." Then you can run the script by using the command bash script.sh or sh script.sh. Another ... Read More

There are several ways to run a script or command as another user in Linux. One way is to use the "su" command, which stands for "switch user." For example, to run a command as the user "john, " you would use the following syntax: "su john -c 'command'" Another way to run a command as another user is to use the "sudo" command, which stands for "superuser do." This command allows a user with proper permissions to run a command with the privileges of another user, typically the root user. For example, to run a command as the root ... Read More

There are several ways to run a script on startup in Linux, depending on your specific distribution and the type of script you are trying to run. Using systemd − On systems that use systemd, you can create a systemd service file for your script and configure it to run on startup. Using cron − You can use the cron daemon to schedule your script to run at startup. You can add a line to the cron table (crontab) to run your script at a specific time on startup. Using init.d − On systems that use the older init.d ... Read More

In a shell script, you can store a command in a variable by using the syntax − variable_name="command" For example − current_date="date" You can then execute the command stored in the variable by prefixing it with $ − $current_date This will execute the command date. Storing the Command in an Array In a shell script, you can store a command in an array by using the syntax minus; array_name=( "command1" "command2" "command3" ) For example − commands=( "ls -l" "pwd" "date" ) You can then execute the commands stored in the array by using a ... Read More

The default editor for crontab on Linux is the vi editor. However, this can be changed by setting the VISUAL or EDITOR environment variable to the desired editor before running the crontab command. For example, to use nano as the editor for crontab, the command would be − export VISUAL=nano; crontab -e or export EDITOR=nano; crontab -e This will open the crontab file in nano for editing. Editor in Linux An editor in Linux is a program that allows users to create, view, and modify text files. There are many different text editors available for Linux, each with ... Read More

Linux monitoring refers to the process of tracking and analyzing various aspects of a Linux system's performance, such as CPU usage, memory usage, disk usage, network traffic, and system uptime. The goal of Linux monitoring is to detect and diagnose any issues that may be impacting the performance or stability of the system, and to identify and correct problems before they become critical. Network Monitoring Tools Some common network monitoring tools for Linux include − nload − is a command-line tool for monitoring network traffic on a Linux system. Speedometer − is a simple tool but with a different ... Read More

In Linux, the command history is a record of previously executed commands. The command history is stored in a file called . bash_history, which is located in the home directory of each user. The history command can be used to view the command history, and the history command can also be used with other commands, such as grep, to search for specific commands in the history. The commands in the history are assigned a number, which can be used to quickly execute a previous command by prefixing it with an exclamation mark (!). For example, typing "!123" will execute the ... Read More

A simple service in Linux is a program that runs in the background and performs a specific function or set of functions. These programs can be started automatically at boot time, and can be controlled using the command line or through a system service manager such as systemd or Upstart. To create a simple service in Linux, you would first write the program that performs the desired function. This program should be designed to run in the background and to continue running even after the terminal window or SSH session is closed. Next, you would create a script that can ... Read More

There are several ways to display a GUI notification from a shell script in Linux, but one common method is to use the notify-send command. This command is part of the libnotify library and is typically pre-installed on most Linux distributions. An example of how to use notify-send to display a notification with a title of "Hello" and a message of "World" is − notify-send "Hello" "World" You can use the command in your shell script by simply adding the command to it, or assign the notification text to a variable and use it message="This is your reminder" ... Read More