Leetcode 192. Word FrequencyLinux三剑客sed，grep,awk用法

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

题目链接：https://leetcode.com/problems/word-frequency/

# Read from the file words.txt and output the word frequency list to stdout.
cat words.txt | tr ' ' '\n' |sort| grep .| uniq -c | sort -r -n -k 1| awk '{print $2,$1}' 

或者

# Read from the file words.txt and output the word frequency list to stdout.
awk '{ for (i=1; i<=NF; i++) { ++D[$i]; } } END { for (i in D) { print i, D[i] } } ' words.txt | sort -nr -k 2

或者

# Read from the file words.txt and output the word frequency list to stdout.
tr ' ' '\n' < words.txt | sort | uniq -c | sort -nr | awk 'NF>1{print $2" "$1}'