008_standard_lib_os

#!/usr/bin/env python
# Author:liujun

#The standard library

import os
res = os.system("ls -l")  #used to execute commands and doesn't return anything
print("res----",res)  #the value of res is 0,because os.system doesn't return anything


res = os.popen("ls -l").read()
    #used to execute commands and return the result of executing the command
    # The read() is needed here
print("popen ----- ",res)