自己用了excel里面的vlookup。解决了

不知道这个能否满足您要求：

data have(drop=pid start length);
infile cards truncover;
input web $100.;
retain pid;
if _n_=1 then pid=prxparse('/^https?:\/\/\w+\.\w+\.\w+(?=\/)/');
call prxsubstr(pid,web,start,length);
  if start>0 then do;
    site=substr(web,start,length);
        output;
  end;
cards;
http://www.baidu.com/index.php?tn=monline_5_dg
https://communities.sas.com/thread?start=20
https://bbs.pinggu.org/forum-68-1.html
https://www.google.com/webhp?source=search_app
;
run;