leetcode-shell-192. 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

题意：统计词的频率
思路：
最开始想创建数组来记录词出现的频率，但是遍历成本高，后来看了别人的方法，使用awk工具就可以
最终shell脚本：
cat words.txt | tr -s ' ' '\n' | sort | uniq -c | sort -rn | awk '{print $2" "$1}'

tr 表示用什么切分单词，有点儿像split函数，后面跟空格和回车，表示我们通过空格和回车切分单词
sort 用来排序
uniq去重，-c用来统计个数
sort -rn -rn表示用数值倒序排序