Efficient Python Daemon

Question

I was curious how you can run a python script in the background, repeating a task every 60 seconds. I know you can put something in the background using &, is that effeictiv

Answer 1

I think your idea is pretty much exactly what you want. For example:

import time

def do_something():
    with open("/tmp/current_time.txt", "w") as f:
        f.write("The time is now " + time.ctime())

def run():
    while True:
        time.sleep(60)
        do_something()

if __name__ == "__main__":
    run()

The call to time.sleep(60) will put your program to sleep for 60 seconds. When that time is up, the OS will wake up your program and run the do_something() function, then put it back to sleep. While your program is sleeping, it is doing nothing very efficiently. This is a general pattern for writing background services.

To actually run this from the command line, you can use &:

$ python background_test.py &

When doing this, any output from the script will go to the same terminal as the one you started it from. You can redirect output to avoid this:

$ python background_test.py >stdout.txt 2>stderr.txt &