Re: [2.4.2/Linux] Getting Python to fork?
On Mon, 04 Feb 2008 16:40:01 +0100, Rolf van de Krol [EMAIL PROTECTED] wrote: To create a deamon, you indeed need to fork two times. Do I really need this much complication just to exit the script and let a child handle the pop-up? I've changed this line, and the parent still doesn't return, and the script waits until the child ends before resuming to the next step: if os.fork(): #BAD? sys.exit(0) os._exit(0) else: Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: [2.4.2/Linux] Getting Python to fork?
On 2008-02-04, Christian Heimes [EMAIL PROTECTED] wrote: Jon Ribbens wrote: Why? I don't think you do. Neither does BSD daemon.c or glibc daemon.c The problem is well documented at http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66012 OK I understand what is being said here, although it seems a bit unlikely (daemon process opens a tty), but what is puzzling me is why, if it's so necessary, does neither Linux nor *BSD do this in their daemon() functions? It would seem surprising if the operating system authors don't know how to make a daemon process in their own OS ;-) -- http://mail.python.org/mailman/listinfo/python-list
Re: [2.4.2/Linux] Getting Python to fork?
To create a deamon, you indeed need to fork two times. For more information and a working example see: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/278731 . I'm quite sure this works, because I used it several times to create a deamon. Jon Ribbens wrote: On 2008-02-04, Christian Heimes [EMAIL PROTECTED] wrote: Although bear in mind it's pretty UNIX-y. IIRC you have to fork a second time after you have changed the working dir and created a new session group. Why? I don't think you do. Neither does BSD daemon.c or glibc daemon.c -- http://mail.python.org/mailman/listinfo/python-list
Re: [2.4.2/Linux] Getting Python to fork?
On 2008-02-04, Gilles Ganault [EMAIL PROTECTED] wrote: I need to launch a Python script, and fork it so that the calling script can resume with the next step will the Python script keeps running. I tried those two, but they don't work, as the calling script is stuck until the Python script ends: This should work I believe: if os.fork(): os._exit(0) os.setsid() os.chdir(/) fd = os.open(/dev/null, os.O_RDWR) os.dup2(fd, 0) os.dup2(fd, 1) os.dup2(fd, 2) if fd 2: os.close(fd) # do stuff Although bear in mind it's pretty UNIX-y. -- http://mail.python.org/mailman/listinfo/python-list
Re: [2.4.2/Linux] Getting Python to fork?
On 2008-02-04, Rolf van de Krol [EMAIL PROTECTED] wrote: To create a deamon, you indeed need to fork two times. For more information and a working example see: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/278731 . I'm quite sure this works, because I used it several times to create a deamon. That doesn't mean it works. That just means it hasn't failed while you were watching. (Not that I am saying it's necessarily wrong, I'm just saying that it worked when I tried it is a very bad way of deciding if something is correct code.) -- http://mail.python.org/mailman/listinfo/python-list
Re: [2.4.2/Linux] Getting Python to fork?
Jon Ribbens wrote: This should work I believe: if os.fork(): os._exit(0) os.setsid() os.chdir(/) fd = os.open(/dev/null, os.O_RDWR) os.dup2(fd, 0) os.dup2(fd, 1) os.dup2(fd, 2) if fd 2: os.close(fd) # do stuff Although bear in mind it's pretty UNIX-y. IIRC you have to fork a second time after you have changed the working dir and created a new session group. Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: [2.4.2/Linux] Getting Python to fork?
Jon Ribbens wrote: Why? I don't think you do. Neither does BSD daemon.c or glibc daemon.c The problem is well documented at http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66012 The second fork _is_ necessary, Jonathan Bartlett, 2003/10/31 The first fork accomplishes two things - allow the shell to return, and allow you to do a setsid(). The setsid() removes yourself from your controlling terminal. You see, before, you were still listed as a job of your previous process, and therefore the user might accidentally send you a signal. setsid() gives you a new session, and removes the existing controlling terminal. The problem is, you are now a session leader. As a session leader, if you open a file descriptor that is a terminal, it will become your controlling terminal (oops!). Therefore, the second fork makes you NOT be a session leader. Only session leaders can acquire a controlling terminal, so you can open up any file you wish without worrying that it will make you a controlling terminal. So - first fork - allow shell to return, and permit you to call setsid() Second fork - prevent you from accidentally reacquiring a controlling terminal. -- http://mail.python.org/mailman/listinfo/python-list
Re: [2.4.2/Linux] Getting Python to fork?
On 2008-02-04, Christian Heimes [EMAIL PROTECTED] wrote: Although bear in mind it's pretty UNIX-y. IIRC you have to fork a second time after you have changed the working dir and created a new session group. Why? I don't think you do. Neither does BSD daemon.c or glibc daemon.c -- http://mail.python.org/mailman/listinfo/python-list
Re: [2.4.2/Linux] Getting Python to fork?
Gilles Ganault wrote: Hello I need to launch a Python script, and fork it so that the calling script can resume with the next step will the Python script keeps running. I tried those two, but they don't work, as the calling script is stuck until the Python script ends: sys.stdout = open(os.devnull, 'w') = #if os.fork(): pid = os.fork() if pid 0: sys.exit(0) = Should I use another library to do this? Thank you. What OS? Stuck how? I you want both processes to execute, why do you call sys.exit? I don't think you've shown enough code to tell what you are doing right or wrong. Try this: pid = os.fork() if pid: # Original fork continues here # pid is child's process id # ... so onwards with the next step # If it needs to wait for the child to complete, it can call os.waitpid else: # New fork continues here, independently of the original process # doing whatever the fork was create for Gary Herron -- http://mail.python.org/mailman/listinfo/python-list
