Write a bash script to calculate the frequency of each word in a text file words.txt.

For simplicity sake, you may assume:

• words.txt contains only lowercase characters and space ' ' characters.
• Each word must consist of lowercase characters only.
• Words are separated by one or more whitespace characters.

Example:

Assume that words.txt has the following content:

the day is sunny the the

the sunny is is

Your script should output the following, sorted by descending frequency:

the 4

is 3

sunny 2

day 1

统计单词出现的次数，并倒序输出

awk '{for(i=1;i<=NF;i++)res[$i]++}END{for(var in res)print var , res[var] | "sort -k 2 -nr"}' words.txt