Apportez le programme Python actuel à l'arrière-plan
Un script Python imprime des informations à l'écran, puis devrait aller en arrière-plan.
Comment faire cela à partir du script lui-même?
22
demandé sur
Sven Marnach
2011-05-12 12:09:37
2 réponses
Mise à Jour: Pour bien daemonize votre processus, utilisez daemonize.
Réponse originale : puisque le shell attend la fin de votre processus, le processus principal doit se terminer. Vous pouvez utiliser os.fork()
pour bifurquer un processus enfant et sys.exit()
du processus parent:
import os
import sys
if os.fork():
sys.exit()
# Child code goes here
19
répondu
Sven Marnach
2017-10-11 09:37:13
Copier le code associé à partir de Créer un démon de la manière Python ; Veuillez lire les commentaires sur la raison pour laquelle ce code est assez pensé.
def createDaemon():
"""Detach a process from the controlling terminal and run it in the
background as a daemon.
"""
try:
# Fork a child process so the parent can exit. This returns control to
# the command-line or shell. It also guarantees that the child will not
# be a process group leader, since the child receives a new process ID
# and inherits the parent's process group ID. This step is required
# to insure that the next call to os.setsid is successful.
pid = os.fork()
except OSError, e:
raise Exception, "%s [%d]" % (e.strerror, e.errno)
if (pid == 0): # The first child.
# To become the session leader of this new session and the process group
# leader of the new process group, we call os.setsid(). The process is
# also guaranteed not to have a controlling terminal.
os.setsid()
# Is ignoring SIGHUP necessary?
#
# It's often suggested that the SIGHUP signal should be ignored before
# the second fork to avoid premature termination of the process. The
# reason is that when the first child terminates, all processes, e.g.
# the second child, in the orphaned group will be sent a SIGHUP.
#
# "However, as part of the session management system, there are exactly
# two cases where SIGHUP is sent on the death of a process:
#
# 1) When the process that dies is the session leader of a session that
# is attached to a terminal device, SIGHUP is sent to all processes
# in the foreground process group of that terminal device.
# 2) When the death of a process causes a process group to become
# orphaned, and one or more processes in the orphaned group are
# stopped, then SIGHUP and SIGCONT are sent to all members of the
# orphaned group." [2]
#
# The first case can be ignored since the child is guaranteed not to have
# a controlling terminal. The second case isn't so easy to dismiss.
# The process group is orphaned when the first child terminates and
# POSIX.1 requires that every STOPPED process in an orphaned process
# group be sent a SIGHUP signal followed by a SIGCONT signal. Since the
# second child is not STOPPED though, we can safely forego ignoring the
# SIGHUP signal. In any case, there are no ill-effects if it is ignored.
#
# import signal # Set handlers for asynchronous events.
# signal.signal(signal.SIGHUP, signal.SIG_IGN)
try:
# Fork a second child and exit immediately to prevent zombies. This
# causes the second child process to be orphaned, making the init
# process responsible for its cleanup. And, since the first child is
# a session leader without a controlling terminal, it's possible for
# it to acquire one by opening a terminal in the future (System V-
# based systems). This second fork guarantees that the child is no
# longer a session leader, preventing the daemon from ever acquiring
# a controlling terminal.
pid = os.fork() # Fork a second child.
except OSError, e:
raise Exception, "%s [%d]" % (e.strerror, e.errno)
if (pid == 0): # The second child.
# Since the current working directory may be a mounted filesystem, we
# avoid the issue of not being able to unmount the filesystem at
# shutdown time by changing it to the root directory.
os.chdir(WORKDIR)
# We probably don't want the file mode creation mask inherited from
# the parent, so we give the child complete control over permissions.
os.umask(UMASK)
else:
# exit() or _exit()? See below.
os._exit(0) # Exit parent (the first child) of the second child.
else:
# exit() or _exit()?
# _exit is like exit(), but it doesn't call any functions registered
# with atexit (and on_exit) or any registered signal handlers. It also
# closes any open file descriptors. Using exit() may cause all stdio
# streams to be flushed twice and any temporary files may be unexpectedly
# removed. It's therefore recommended that child branches of a fork()
# and the parent branch(es) of a daemon use _exit().
os._exit(0) # Exit parent of the first child.
23
répondu
tzot
2011-05-12 10:01:52