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.

For 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

可以使用关联数组实现

后面需要按频数降序排序可以使用sort实现

• -n 表示按照数值排序，而不是默认的字典排序
• -t & -k 其中-t指定字段分隔符，-k表示排序的字段
• -r 表示降序。

代码为:

#!/bin/bash
declare -A count
for word in $(cat words.txt)
do
	let count[$word]++
done
(for word in ${!count[@]}
do
	printf "%s %d\n" $word ${count[$word]}
done) | sort -n -r -t ' ' -k 2