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Linux nohup Command: Run Background Commands Away From The Terminal

The nohup command is a Linux utility used to run a command or process in the background while ignoring the hangup (SIGHUP) signal. This allows the process to continue running even after the user logs out or the terminal is closed. In this tutorial, we'll discuss how to use the nohup command to run processes in the background.

Basic Usage

The basic syntax of the nohup command is:

nohup command [arguments] &

Replace command with the name of the process you want to run, and arguments with any required command-line arguments for the process. The & at the end is important, as it tells the shell to run the command in the background.

Run a process in the background:
To run a process in the background using nohup, simply use the nohup command followed by the command you want to run. For example, to run a command called my_command in the background, use the following command:
```
nohup my_command &
```
This command will start the process in the background and ignore the hangup signal. You should see output similar to this:
```
nohup: ignoring input and appending output to 'nohup.out'
```
By default, the nohup command redirects the standard output (STDOUT) and standard error (STDERR) of the process to a file called nohup.out in the current directory. If the file does not exist, it will be created; otherwise, the output will be appended to the existing file.
Redirect output to a different file:
If you want to redirect the output of the process to a different file, you can use the output redirection syntax of the shell. For example, to redirect the output of my_command to a file called output.log, use the following command:
```
nohup my_command > output.log 2>&1 &
```
This command redirects both STDOUT and STDERR to the output.log file.

Managing Background Processes

To manage the background processes started with nohup, you can use the jobs, fg, and bg commands:

List background processes:
To list all the background processes running in the current shell, use the jobs command:
```
jobs
```
Bring a background process to the foreground:
To bring a background process to the foreground, use the fg command followed by the job number. You can find the job number by running the jobs command. For example, to bring job number 1 to the foreground, use the following command:
```
fg %1
```
Move a foreground process to the background:
To move a foreground process to the background, first suspend the process by pressing Ctrl+Z. Then, use the bg command followed by the job number to move the process to the background. For example, to move job number 1 to the background, use the following command:
```
bg %1
```

Conclusion

The nohup command is a useful tool for running processes in the background on Linux systems. It allows you to start long-running tasks without the need to keep the terminal open, and it helps to ensure that your processes are not interrupted when you log out or close the terminal. By understanding the nohup command and related process management commands, you can effectively manage background tasks on your Linux system.

How to use nohup to run commands in the background: Use nohup to run a command that continues running even after you log out. For example:
```
nohup ./my_command &
```
Running background processes with nohup in Unix-like systems: Execute a command in the background using nohup. This allows the command to keep running even if the terminal is closed:
```
nohup ./background_command &
```
Keeping commands running after terminal exit using nohup: Ensure a command keeps running after the terminal exit by using nohup:
```
nohup ./persistent_command &
```
Using nohup for long-running processes in Linux: For long-running processes, use nohup to prevent them from being terminated when the terminal is closed:
```
nohup ./long_running_process &
```
Advanced options for the nohup command in Linux: Explore advanced options with nohup. For example, redirecting output to a file:
```
nohup ./my_command > output.log &
```
Detaching processes with nohup in the terminal: nohup can be used to detach a process from the terminal. For instance:
```
nohup ./detached_process &
```
Linux nohup vs disown: differences and use cases: While both nohup and disown can be used to disassociate a process from the terminal, nohup is typically used when starting a process, while disown is used on an already running process. Example:
```
nohup ./start_process &   # Use nohup to start
disown -h %1             # Use disown on a running process
```
Managing background tasks with nohup in the terminal: Manage background tasks effectively using nohup. Start a process in the background and allow it to continue running:
```
nohup ./background_task &
```