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。
原文：http://www.cnblogs.com/xiaoxian1369/p/5348645.html