[root@pangu icai]# cat  words.txt
how many cans can a canner can if a canner can can cans
a canner can can as many cans as a canner can if a canner can can a can
a canner can can as many cans as a canner can cans

[root@pangu icai]# cat words.txt |tr  ' '  '\n'|sort |uniq -c|sort -r
      8 a
      7 canner
      5 cans
      4 as
      3 many
      2 if
      1 how
     13 can
[root@pangu icai]# cat words.txt |tr  ' '  '\n'|sort |uniq -c|sort -nr
     13 can
      8 a
      7 canner
      5 cans
      4 as
      3 many
      2 if
      1 how

关于解题：
https://discuss.leetcode.com/topic/87252/solve-this-problem-in-linux-style