thread and process

[Carl Banks]

On Saturday, August 13, 2011 2:09:55 AM UTC-7, 守株待兔 wrote:
> please see my code:
> import os
> import  threading
> print  threading.currentThread()  
> print "i am parent ",os.getpid()
> ret  =  os.fork()
> print  "i am here",os.getpid()
> print  threading.currentThread()
> if  ret  ==  0:
>          print  threading.currentThread()
> else:
>         os.wait()
>         print  threading.currentThread()
>         
>         
> print "i am runing,who am i? ",os.getpid(),threading.<WBR>currentThread()
> 
> the output is:
> <_MainThread(MainThread, started -1216477504)>
> i am parent  13495
> i am here 13495
> <_MainThread(MainThread, started -1216477504)>
> i am here 13496
> <_MainThread(MainThread, started -1216477504)>
> <_MainThread(MainThread, started -1216477504)>
> i am runing,who am i?  13496 <_MainThread(MainThread, started -1216477504)>
> <_MainThread(MainThread, started -1216477504)>
> i am runing,who am i?  13495 <_MainThread(MainThread, started -1216477504)>
> it is so strange that  two  different  processes  use one  mainthread!!


They don't use one main thread; it's just that each process's main thread has the same name.  Which makes sense: when you fork a process all the data in the process has to remain valid in both parent and child, so any pointers would have to have the same value (and the -1216477504 happens to be the value of that pointer cast to an int).


Carl Banks