Python spawn off a child subprocess, detach, and exit

Python spawn off a child subprocess, detach, and exit

To spawn a child subprocess in Python, detach it from the parent process, and then exit the parent process, you can use the subprocess module. You can use the subprocess.Popen class to start the child process and the os._exit function to exit the parent process without waiting for the child process to complete. Here's an example:

import subprocess import os # Command to run in the child process (replace with your own command) command = ["python", "child_script.py"] # Start the child process and detach it subprocess.Popen(command, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, stdin=subprocess.DEVNULL, close_fds=True) # Exit the parent process immediately without waiting for the child process os._exit(0)

In this example:

  1. Replace ["python", "child_script.py"] with the command you want to run in the child process. You can specify the command as a list of arguments, where the first element is the executable and the subsequent elements are the command-line arguments.

  2. We use subprocess.Popen to start the child process. We redirect the standard input, standard output, and standard error streams to subprocess.DEVNULL to detach the child process from the parent process. The close_fds=True argument ensures that file descriptors are closed in the child process.

  3. Finally, we use os._exit(0) to exit the parent process immediately without waiting for the child process to complete.

Please note that detaching a child process and exiting the parent process in this way can leave the child process running independently. Be sure to handle any necessary cleanup or error handling in your child process as needed.

Examples

  1. "How to spawn a detached child subprocess in Python"

    • This query explores how to create a subprocess that continues to run even after the parent process exits.
    import subprocess # Spawn a detached subprocess process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], start_new_session=True) print("Subprocess started:", process.pid)

  2. "Python: creating a child process that runs independently"

    • This query examines how to create a child process that runs independently of the parent process.
    import os import subprocess # Create a child process that runs independently if os.name == 'posix': # Use setsid to create a new session process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], preexec_fn=os.setsid) else: process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"]) print("Independent subprocess started:", process.pid)

  3. "Python subprocess: spawn, detach, and exit"

    • This query explores how to spawn a subprocess, detach it, and then exit the parent process while the child process continues to run.
    import subprocess import os # Spawn a detached subprocess and then exit the parent process process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], preexec_fn=os.setsid) print("Parent process exiting, subprocess running:", process.pid)

  4. "Python: create a background process and exit"

    • This query discusses creating a subprocess that runs in the background while the parent process exits.
    import subprocess import os # Spawn a background process process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], preexec_fn=os.setsid) # Parent process exits print("Background process running, parent exiting:", process.pid)

  5. "How to spawn a subprocess that continues after parent exits in Python"

    • This query explores creating a subprocess that keeps running after the parent process exits.
    import subprocess import os # Spawn a subprocess that continues after parent exits process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], preexec_fn=os.setsid) # Simulate parent process exit print("Parent exiting, subprocess will continue:", process.pid)

  6. "Python: creating a child process that runs detached from parent"

    • This query describes how to create a child process that is detached from the parent.
    import subprocess import os # Create a detached subprocess if os.name == 'posix': # Detach the process by creating a new session process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], preexec_fn=os.setsid) else: process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"]) print("Detached subprocess running:", process.pid)

  7. "Python: start a subprocess that doesn't block the parent"

    • This query explores creating a subprocess that doesn't block the parent process.
    import subprocess import os # Start a subprocess that doesn't block the parent process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], start_new_session=True) print("Subprocess running, parent not blocked:", process.pid)

  8. "Python: spawn a subprocess with separate output"

    • This query describes creating a subprocess that has its own output streams, allowing the parent process to exit without affecting the child process.
    import subprocess import os # Spawn a subprocess with separate output streams process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], preexec_fn=os.setsid, stdout=subprocess.PIPE, stderr=subprocess.PIPE) print("Subprocess with separate output running:", process.pid)

  9. "Python: spawn a child process with environment isolation"

    • This query explores creating a subprocess with a separate environment, isolating it from the parent process.
    import subprocess import os # Create a child process with isolated environment new_env = os.environ.copy() new_env["SOME_VARIABLE"] = "some_value" process = subprocess.Popen(["python3", "-c", "import time; time.sleep(10)"], preexec_fn=os.setsid, env=new_env) print("Subprocess with isolated environment running:", process.pid)

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