import os

print(‘Process (%s) start...‘ % os.getpid())
# Only works on Unix/Linux/Mac:
pid = os.fork()
print ("haha")
if pid == 0:
    print(‘I am child process (%s) and my parent is %s.‘ % (os.getpid(), os.getppid()))
else:
    print(‘I (%s) just created a child process (%s).‘ % (os.getpid(), pid))


 
"""
haha
haha
Process (876) start...
I (876) just created a child process (877).
I am child process (877) and my parent is 876.
"""

執行到os.fork()時，發起fork系統調用，操作系統復制父進程得到子進程。fork系統調用完畢，返回給父進程子進程的id號，返回給子進程0，然後父子進城開始執行。我們可以看到haha被打印了兩次，更加說明了子進程是復制父進程得來的

以python代碼解釋fork系統調用