【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?

【193】Valid Phone Numbers    

【194】Transpose File   

【195】Tenth Line