I’ve been battling some unusual web traffic on my site. I get thousands of hits every day from random IP addresses and all of them look something like this:

GET /newsletter/consulting/otherlinks/public/support/support/default.html

The string is made up of actual folder names on my site, but they are combined in random order and a random page is on the end. I am told this is penetration testing by a hacker bot.  Great. 

While working on this problem I wanted a way to count the number of slashes in each request. Crystal doesn’t have a direct function for doing that, but after giving it some thought I found a relatively simple solution. I could:

• calculate the length of the string,
• replace all the slashes with an empty string (“”)
• recalculate the length of the shorter string.
• Subtract one length from the other to get the difference

That can even be used to count occurrences of a multiple character string. You would just have to divide the character difference by the number of characters in the target string. So I turned this into a generic formula (see below). You can plug in your field name and target string in the first two lines and it does the rest:

Local stringVar Field := {Table.Field};
Local stringVar Target := '/';Local numberVar x := Length(Field);
Local numberVar y := length (Replace (Field, Target, ''));
Local NumberVar z := length (Target); 
(x-y) / z