import os
import time
ret = os.fork() # 创建子线程

if ret ==0: # 子进程中返回值为0，父进程>0
    while True:
        print(‘......1......‘)
        time.sleep(1)

else:
    while True:
        print(‘......2......‘)
        time.sleep(1)

import os
import time
ret = os.fork()

if ret ==0:
    print(‘......1......‘)

else:
    print(‘......2......‘)


ret = os.fork()

if ret ==0:
    print(‘......11......‘)

else:
    print(‘......22.....‘)

import os
import time
ret = os.fork()

if ret ==0:
    print(‘......1......‘)

else:
    print(‘......2......‘)


    ret = os.fork()

    if ret ==0:
        print(‘......11......‘)

    else:
        print(‘......22.....‘)