our plan as follow:

1.list all linux system api deadline :12/16 : overview.txt

2.learn a function every day:include

   1):mkdir for every function,for example func_****
   2):create a txt with official description for that function
   3):mkdir for us to use,the directory structure can be like this as fellow:

    -func_***/
    ----description.txt
    ----practice/