os.system() or os.execv() w/stdout redirect and PID tracking

[Gordon McMillan]

Michael Olivier writes:
 
> What's the best way from a python program to start another program
> in the background and: - redirect stdout/stderr to a file - get the
> process ID of the started program.
> 
> It seems that:
> 
> - os.system() call can start a program in the background, but
> doesn't return the pid (process ID) of the started program --
> returns 0
/snip/
> - if I call os.fork() and then os.execv(), the pid is trackable, but
> I don't know a way to redirect stdout/stderr

Something like this (snipped class method from working code):

 def startChild(self):
   c2pread, c2pwrite = os.pipe()
   self.pid = os.fork()
   if self.pid == 0:		#Child
     os.close(1)			#close stdout
     if os.dup(c2pwrite) != 1:
       sys.stderr.write("bad write dup!\n")
     try:
       os.execv("/usr/local/bin/python", 
                ("/usr/local/bin/python",
                 "receiver.py", 
                 "%s_GATE"%self.thissite))
     finally:
       print "child could not start"
       os._exit(1)
   print "child pid =", self.pid
   os.close(c2pwrite)


- Gordon