Get a word's individuality! I love /usr/share/dict/words; it's so handy! I use it for all my programs, whenever I can! You're going to take advantage of this ever so useful file to use, by testing a word's individuality.



Input


A word; defined in this challenge as any string of characters
/usr/share/dict/words in some format; you may hard code it, read from disk, assume it as a second argument, whatever makes the most sense in your challenge   


Output


A words individuality (see below)


A word's individuality is derived from the following equation:

&lt;the number of words for which it is a substring&gt; / &lt;length of the word&gt;


Let's take a look at an example:
hello. There are 12 words which have the substring hello in them, divided by 5 (hello's length), and hello's individuality is 12/5 or 2.4


P.S. This is codegolf, so the lower the individuality score, the more individual

Because individuality is a long word, your program must be as short as possible

Good Luck!


Test Cases

You can use this convenient Node.js script, which fits the challenge requirements to fit your code. It is also how I generated the test cases:

var fs = require("fs");
var word = process.argv[2];

process.stdout.write("Reading file...")
fs.readFile("/usr/share/dict/words", function(err, contents) {
  console.log("Done")
  if (err) throw err;

  words = contents.toString().split("\n");

  var substrings = words.filter(w =&gt; w.indexOf(word) &gt; -1).length;
  var length     = word.length;

  console.log(`${word} =&gt; ${substrings} / ${length} = ${substrings / length}`)
})


Test Cases:

hello =&gt; 12 / 5 = 2.4
individuality =&gt; 1 / 13 = 0.07692307692307693
redic =&gt; 52 / 5 = 10.4
ulous =&gt; 200 / 5 = 40
challen =&gt; 15 / 7 = 2.142857142857143
ges =&gt; 293 / 3 = 97.66666666666667
hidden =&gt; 9 / 6 = 1.5
words =&gt; 12 / 5 = 2.4
aside =&gt; 8 / 5 = 1.6
Bash, 41, 39, 34, 33, 26 bytes
EDIT:

Converted from function to a script
One byte off by removing the ignore case flag
Replaced wc -l with grep -c, saving 5 bytes. Thanks @Riley !

A rather trivial solution in bash + coreutils
Golfed
bc -l&lt;&lt;&lt;`grep -c $1`/${#1}

Test
&gt;cat /usr/share/dict/words| ./test ulous
7.60000000000000000000

&gt;grep -i ulous /usr/share/dict/words | wc -l
38