Python_2_7_daemonize_script.py

# -*- coding:utf-8 -*-
import os
import sys
import atexit
import signal
import codecs


def daemonize(pidfile, stdin='/dev/null',
              stdout='/dev/null',
              stderr='/dev/null'):
    if os.path.exists(pidfile):
        raise RuntimeError('Already Running')

    try:
        if os.fork() > 0:
            raise SystemExit(0)
    except OSError as e:
        raise RuntimeError('Fork #1 failed.')

    os.chdir('/')
    os.umask(0)
    os.setsid()

    try:
        if os.fork() > 0:
            raise SystemExit(0)
    except OSError as e:
        raise RuntimeError('Fork #2 failed.')

    sys.stdout.flush()
    sys.stderr.flush()

    _stdin = codecs.open(stdin, 'r', encoding='utf-8')
    os.dup2(_stdin.fileno(), sys.stdin.fileno())

    _stdout = codecs.open(stdout, 'w+', encoding='utf-8')
    os.dup2(_stdout.fileno(), sys.stdout.fileno())

    _stderr = codecs.open(stderr, 'w+', encoding='utf-8')
    os.dup2(_stderr.fileno(), sys.stderr.fileno())

    with codecs.open(pidfile, 'w', encoding='utf-8') as f:
        f.write(str(os.getpid()))

    atexit.register(lambda: os.remove(pidfile))

    def sigterm_handler(signo, frame):
        raise SystemExit(1)

    signal.signal(signal.SIGTERM, sigterm_handler)


def main():
    sys.stdout.write('Daemon start with PID {}\n'.format(os.getpid()))

    '''
      Call what you want to daemonize here.
    '''

def execute_from_cli(argv):
    PIDFILE = '/path/to/your/pid/file.pid'

    if len(argv) != 2:
        print('Usage : {} [start|stop]'.format(argv[0], file=sys.stderr))
        raise SystemExit(1)

    if argv[1] == 'start':
        try:
            daemonize(PIDFILE, stdout='/path/to/redirect/stdout',
                      stderr='/path/to/redirect/stderr')
        except RuntimeError as e:
            sys.stderr.write(e.message)
            raise SystemExit(1)

        main()

    elif argv[1] == 'stop':
        if os.path.exists(PIDFILE):
            with codecs.open(PIDFILE, 'r', encoding='utf-8') as f:
                os.kill(int(f.read()), signal.SIGTERM)
        else:
            with codecs.open(sys.stderr) as f:
                f.write('Not running.')
            raise SystemExit(1)
    else:
        print('Unknown command {!r}'.format(sys.argv[1], file=sys.stderr))
        raise SystemExit(1)