How to create a frequency list of every word in a file?

Question

I have a file like this:

This is a file with many words.
Some of the words appear more than once.
Some of the words only appear one time.

I

Answer 1

If I have the following text in my file.txt.

This is line number one
This is Line Number Tow
this is Line Number tow

I can find the frequency of each word using the following cmd.

 cat file.txt | tr ' ' '\n' | sort | uniq -c

output :

  3 is
  1 line
  2 Line
  1 number
  2 Number
  1 one
  1 this
  2 This
  1 tow
  1 Tow