对一个文件显示双单词

1，首先有一个文件data tao@debian6:~$ cat data hello hello about is is is are you ok be yes no NO are are jerry jerry jerry JERRY She's my girlfriend 2，创建一个管道线，显示所有的双单词，如hello hello tao@debian6:~$ cat data | tr -cs [:alpha:]\' "\n" |uniq  -c |grep 2|awk '{print $2}' hello are