bash: 1: tr -cs A-Za-z '\n' | 2: tr A-Z a-z | 3: sort | 4: uniq -c | 5: sort -rn | 6: sed ${1}q
via leancrew.com
"Read a file of text, determine the n most frequently used words, and print out a sorted list of those words along with their frequencies." — by the guy who invented pipes.