Forking is based on the notion of copying programs: when a program calls the fork routine, the

operating system makes a new copy of that program and its process in memory and

starts running that copy in parallel with the original. Some systems don’t really copy

the original program (it’s an expensive operation), but the new copy works as if it were

a literal copy.

 

all forked processes run independently and in parallel under the operating system’s control, and

children may continue to run after their parent exits.

 

os.fork built-in function. Because this function

generates a copy of the calling program, it returns a different value in each copy: zero

in the child process and the process ID of the new child in the parent

import osdef child():    print("hello from child", os.getpid())    os.exit(0)def parent():    while True:        newpid=os.fork()        if newpid==0:            child()        else:            print("hello from parent",os.getpid(), newid)        if input()=='q': breakparent()

 

*fork cannot work well in typical win; but can work under cygwin