#!/usr/bin/env bash
 readWords() {
    declare -i int="$1"

    (( int == 0 )) && {
       printf "%s\n" "$int is 0, cant find 0 words"
       return 1
    }

    while read getWords;do
       if [[ ${#getWords} -eq $int ]];then
         printf "%s\n" "$getWords"
       fi
   done < /usr/share/dict/words
}

readWords 20