Shell练习 统计单词个数，降序排列

原文：https://leetcode.com/problems/word-frequency/
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

简单点就是说给你一个文件，里面是又空格【可以有多个】分割好的单词【都是小写】，请统计一下不同单词的个数，并降序输出。

将单词记录到数组中，之后遍历输出，使用sort排序，指定第2列按数字降序，即可。

答案：

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

使用sort排序，指定哪一列使用-k，后面跟数字，按数字进行排序，使用-n，降序排列使用-r。