Of course! The term "nohup print" in Python usually means you want to run a Python script in the background, so it doesn't stop when you close your terminal (SSH session), and you want to see its output (the print statements) either in real-time or saved to a file.

Let's break this down into two main scenarios:

1. The Easy & Modern Way (Recommended): Using a terminal multiplexer like tmux or screen. This gives you a persistent, interactive session.
2. The Classic Unix Way: Using the nohup command. This is simpler for a one-off command but less interactive.

Scenario 1: The Easy & Modern Way (tmux or screen)

This is the best approach for long-running scripts where you might want to check on their progress, stop them, or see live output.

Using tmux (Terminal Multiplexer)

tmux is a powerful tool that lets you create multiple persistent terminal sessions inside one terminal window.

Step 1: Create a new tmux session Open your terminal and run:

tmux new -s my_python_session

This creates a new session named my_python_session and you'll be inside it.

Step 2: Run your Python script Now, inside this tmux session, simply run your Python script as you normally would. The print statements will appear on your screen.

python your_script.py

Step 3: Detach from the session To leave the session running in the background, press the tmux detach key combination: Ctrl-b then d.

Your script is now running in the background, and you can safely close your terminal or SSH connection.

Step 4: Re-attach to the session later To see the output and re-attach to your running session, use:

tmux attach -t my_python_session

You will see the terminal exactly as you left it, including any new print output that has occurred.

Bonus: Splitting the screen Inside a tmux session, you can split the window to see your output and run other commands.

• Split vertically: Ctrl-b then
• Split horizontally: Ctrl-b then
• Navigate between panes: Ctrl-b then an arrow key.

Using screen

screen is the older, more classic version of tmux with similar functionality.

Step 1: Create a new screen session

screen -S my_python_session

Step 2: Run your Python script

python your_script.py

Step 3: Detach from the session Press the screen detach key combination: Ctrl-a then d.

Step 4: Re-attach to the session later

screen -r my_python_session

Scenario 2: The Classic Unix Way (nohup)

nohup (No Hang Up) is a command that makes a process immune to hangups (i.e., when you log out or close the terminal). By default, it redirects output to a file.

The Basic Command

You can run your Python script directly with nohup.

nohup python your_script.py

What happens here?

1. nohup: The script will continue running after you log out.
2. python your_script.py: Your script is executed.
3. Output Redirection: By default, nohup redirects stdout (where print goes) to a file named nohup.out in the current directory.
4. Backgrounding: The command runs in the background. You'll get your terminal prompt back immediately.

The Modern nohup Command (Recommended)

To have more control, it's best to explicitly redirect both output and errors to a specific file.

nohup python your_script.py > my_output.log 2>&1 &

Let's break this down:

• nohup: Protects the process from being terminated.
• python your_script.py: The command to run.
• > my_output.log: Redirects standard output (stdout) to a file named my_output.log.
• 2>&1: Redirects standard error (stderr, where errors and exceptions go) to the same place as standard output (stdout). This is crucial for capturing all your script's output.
• &: Runs the entire command in the background.

How to check on your script

1. Check the output file: You can tail the log file to see the latest print statements in real-time.

   tail -f my_output.log

   Press Ctrl-c to stop tail.

2. Find the Process ID (PID): To manage the process (e.g., stop it), you need its Process ID (PID).

   ps aux | grep python

   Look for the line with your script. The second column is the PID.

3. Stop the process: Once you have the PID, you can kill it.

   kill <PID>

   For example: kill 12345

Summary Table

Example Python Script

Let's use this simple script for testing. Save it as long_running_task.py.

# long_running_task.py
import time
import datetime
print(f"Script started at: {datetime.datetime.now()}")
for i in range(10):
    print(f"Processing item {i+1}...")
    time.sleep(2) # Wait for 2 seconds
print(f"Script finished at: {datetime.datetime.now()}")

Now you can test any of the methods above with this script. For example, with nohup:

# Run the script in the background
nohup python long_running_task.py > task.log 2>&1 &
# Check the status of the process
ps aux | grep long_running_task
# Watch the output in real-time
tail -f task.log

You will see the print statements appear in your terminal every 2 seconds, even if you open a new SSH session.