unix_daemon.daemon(nochdir=False, noclose=False)

Make process daemon and start to run in the background.

Arguments

If argument 1 ‘nochdir’ is False, the process changes the calling

process’s current working directory to the root directory (“/”);

otherwise, the current working directory is left unchanged.

The default value of the nochdir is False.

If argument 2 ‘noclose’ is False, this function close file descriptors 0,

1 and 2 and redirect them to /dev/null. Even if some of them have been

closed, this function open these file descriptors and redirect to

/dev/null if noclose is False.

The defult value of noclose is False.

Return Value

daemon returns the pid of new process.

Note

This function calls os.fork() internally to detach tty safely.

Be careful to call this function when two or more than two python threads

are running.

Normary, file descriptors 0, 1 and 2 are correspond to stdin, stdout and

stderr. However, even if any of these file discriptors refer to something

else, they will still be closed when argument ‘noclose’ is False.

It is a good idea to call this function before creating any threads and

before opening any files or sockets.

Example

Call unix_daemon.daemon(), then the process starts to run in the backgrond.

import unix_daemon
import os

print('pid: %s\n' % os.getpid())

pid = unix_daemon.daemon()
with open('/tmp/foo', 'a') as f:
    print('pid: %s\n' % os.getpid())
    f.write('new pid: %s\n' % pid)

You can see the process id changes and the 2nd print is not displayed.