I have an ASCII text file. I want to generate a list of all "words" from that file using one or more Ubuntu commands. A word is defined as an alpha-num sequence between delimiters. Delimiters are by default whitespaces but I also want to experiment with other characters like punctuation etc. IN other words, i want to be able to specify a delimiter char set. How do I produce only a unique set of words? What if I also want to list only those words that are at least N characters long?