How do I run a Linux command in the background? Running a Linux command in the background is a simple yet powerful technique that allows you to execute a task while still being able to use the terminal for other commands. This can be particularly useful when running long-running commands or scripts that you don’t want to tie up your terminal.

In this blog post, we will explore the different ways to run a Linux command in the background and how to manage background processes. Whether you’re a beginner or an experienced Linux user, this guide will help you become more efficient and productive in your command line work.

How Do I Run a Command in the Background?

To run a command in the background on a Unix-based system, you can add an ampersand (&) at the end of the command. For example:

command &

This will run the command in the background and return the command prompt immediately, so you can continue to use the terminal. Related article: How Do I Free up Space in Ubuntu in 2023?

You can also use the nohup command, which allows you to run a command even after you’ve logged out of the system. For example:

nohup command &

This will run the command in the background and redirect all output to the file nohup.out, so you can review it later.

How Do I Run a Shell Script in the Background?

To run a shell script in the background, follow these steps:

1. Add an ampersand (&) at the end of the command:

./my_script.sh &

1. Use the nohup command:

nohup ./my_script.sh &

This will run the script in the background and will continue running even if you log out of the terminal.

1. Use the screen command:

screen -dmS my_script ./my_script.sh

This will create a new screen session named “my_script” and run the script in the background. You can detach from the screen session by pressing Ctrl+A, then D. To reattach to the screen session, use the command “screen -r my_script”.

How Do I Run Multiple Commands in the Background?

You can run multiple commands in the background by appending an ampersand (&) at the end of each command. For example, if you want to run the commands “command1” and “command2” in the background, you would enter “command1 & command2” in the command line. This will allow the commands to run simultaneously in the background, and you will be able to continue entering commands in the foreground.

What Is the Difference Between Nohup and &?

Both nohup and & are used to run commands in the background, but they have different functions:

• nohup (no hangup) is used to run a command that will continue running even after the user logs out of the terminal. It also ignores the SIGHUP (hangup) signal, which is sent to a process when its controlling terminal is closed. This means that the process will not terminate when the user logs out or closes the terminal window.
• & is used to run a command in the background, but it does not ignore the SIGHUP signal. This means that the process will terminate when the user logs out or closes the terminal window.

In summary, nohup is used to keep a process running even after the user logs out, while & is used to run a process in the background but it will be terminated when the user logs out.

How Do I Know if a Script Is Running in the Background?

There are a few ways to check if a script is running in the background on a computer. One way is to use the task manager or activity monitor of the operating system to check for any running processes. On Windows, you can press Ctrl + Alt + Delete and click on “Task Manager” to view running processes. On MacOS, you can use the “Activity Monitor” application to view running processes. Another way is to use command line tools such as “ps” or “top” on Linux and Unix systems, or “tasklist” on Windows to view running processes.

Additionally, you can also check the script log files or the system log files if the script is running in the background.

How Do I Prevent a Script From Running in the Background?

There are several ways to prevent a script from running in the background:

1. Use the “nohup” command before running the script. This command prevents the script from being terminated when the terminal is closed.
2. Use the “&” symbol at the end of the script command to run the script in the background, but use the “fg” command to bring it back to the foreground.
3. Use the “disown” command after the script has been started in the background. This command removes the script from the list of background jobs and it will not be able to be brought back to the foreground.
4. Use the “kill” command to terminate the script if it is running in the background.
5. Use a shell script that runs the command and exits immediately after, this way the command runs but the script itself is not running in the background.
6. Using a task scheduler like cron or at to schedule the script to run at a specific time, this way the script will not run in the background.

How Do I Run Multiple Shell Scripts After One?

There are a few ways to run multiple shell scripts after one:

1. Using the “&&” operator: You can use the “&&” operator to run multiple scripts one after the other. For example, if you have two scripts called script1.sh and script2.sh, you can run them in succession by typing:

./script1.sh && ./script2.sh

1. Using a script launcher: You can create a script launcher that runs multiple scripts one after the other. For example, you can create a script called launcher.sh that contains the following code:

#!/bin/bash ./script1.sh ./script2.sh

You can then run the launcher script by typing:

./launcher.sh

1. Using a loop: You can also use a loop to run multiple scripts one after the other. For example, you can create a script called loop.sh that contains the following code:

#!/bin/bash scripts=(script1.sh script2.sh script3.sh) for script in “${scripts[@]}” do ./”$script” done

You can then run the loop script by typing:

./loop.sh

Note: Make sure all the scripts have execute permission before running them. You can give execute permission to a script by running chmod +x scriptname.sh command.

How do I run multiple Bash commands?

There are several ways to run multiple Bash commands:

1. Separate commands with a semicolon (;):

command1; command2; command3

1. Use the && operator:

command1 && command2 && command3

This will run the next command only if the previous command is successful.

1. Use the || operator:

command1 || command2 || command3

This will run the next command only if the previous command fails.

1. Use a script file: Create a script file with the desired commands, and run the script by using the command:

bash script_file.sh

1. Use the command line: You can run multiple commands on the command line by separating them with a new line.

command1 command2 command3

You can also press the up arrow key to access previous commands and edit them as needed.

How Do I Run Two Parallel Commands on Linux?

You can use the “&” symbol to run two commands in parallel in Linux. For example, to run the commands “command1” and “command2” in parallel, you would use the following command:

command1 & command2

This will run both commands at the same time and return control to the command prompt immediately, allowing you to continue working in the terminal while the commands are running.

Alternatively, you can use the “&&” symbol to run command2 only if command1 is successful or ; symbol for run command2 regardless of the outcome of command1

command1 && command2

command1 ; command2

In conclusion, running a Linux command in the background is a useful skill to have in your toolkit as a Linux user. By appending the “&” symbol at the end of a command, you can easily run it in the background and continue using your terminal for other tasks. Another option is to use the “nohup” command, which allows you to run a command even after you log out of the system. Both of these methods can save you time and increase your productivity as a Linux user. It’s always good to have multiple options when it comes to running Linux commands, so it’s worth experimenting with both methods to see which one works best for you. With this knowledge, you can now run commands in the background and multitask like a pro.

The post How Do I Run a Linux Command in the Background? appeared first on EboraTech.