shell/WordFrequency.sh

# Source : https://leetcode.com/problems/word-frequency/
# Author : Hao Chen
# Date   : 2015-03-31

################################################################################## 
# 
# 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
# 
# Note:
# Don't worry about handling ties, it is guaranteed that each word's frequency count is unique.
# 
# [show hint]
# Hint:
# Could you write it in one-line using Unix pipes?
##################################################################################

#!/bin/sh

# Read from the file words.txt and output the word frequency list to stdout.
cat words.txt | tr [:space:] "\n" | sed '/^$/d' | tr '[:upper:]' '[:lower:]'|sort|uniq -c|sort -nr | awk '{ print $2,$1}'