Paste code

#!/usr/bin/awk -f
{
    $0 = tolower($0)    # remove case distinctions
    # remove punctuation
    gsub(/[^[:alnum:]_[:blank:]]/, " ", $0)
    for (i = 1; i <= NF; i++)
        freq[$i]++
}


END {
    sort = "sort -nr"
    for (word in freq)
        printf "%d\t%s\n", freq[word], word | sort
    close(sort)
}