LeetCode（192. Word Frequency）

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.

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

Note:

• Don't worry about handling ties, it is guaranteed that each word's frequency count is unique.
• Could you write it in one-line using Unix pipes?

一、首先考虑用到grep

• -oE：表示将原文本内容变成一个单词一行的存储方式

二、排序sort(这里排序是为了后面好去重)

三、去重并计算单词出现次数

四、再sort排序(-nr表示按数值进行降序排序)

五、再通过awk控制输出方式

cat words.txt |grep -oE '[a-z]+' |sort |uniq -c |sort -nr |awk '{print $2" "$1}'

法二：tr

注意：tr -s：表示如果发现连续字符，就把他们缩减成1个；后面的' ' '\n'是空格和回车：表示把所有空格换成回车。

tr -s ' ' '\n' < words.txt |sort |uniq -c|sort -nr |awk '{print $2" "$1}'

法三：awk

#!/bin/bash

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

参考资料：http://www.cnblogs.com/grandyang/p/5386475.html