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?
#

# Read from the file words.txt and output the word frequency list to stdout.

cat words.txt | tr -s ' \t\n' '\n' | grep -v '^$' | sort | uniq -c | sort -rn | awk '{ print $2, $1 }'