Question:

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.
Hint:Could you write it in one-line using Unix pipes?

Solutions:

tr " " "\n" < words.txt |sed '/^$/d'| sort | uniq -c |sort -r | awk '{print $2,$1}'