You might want to look at the uniq and sort applications.
./yourscript.ksh | sort | uniq
(FYI, yes, the sort is necessary in this command line, uniq only strips duplicate lines that are immediately after each other)
EDIT:
Contrary to what has been posted by Aaron Digulla in relation to uniq‘s commandline options:
Given the following input:
class jar jar jar bin bin java
uniq will output all lines exactly once:
class jar bin java
uniq -d will output all lines that appear more than once, and it will print them once:
jar bin
uniq -u will output all lines that appear exactly once, and it will print them once:
class java