Archived. It is written for Backtrack, and current guidance is to avoid cleaning capture files. Cleaning can remove frames needed to extract hashes from the capture. See Cracking WPA/WPA2. This page is kept for reference and is listed in the Archive.
SmilingWolf, a forum member, has kindly written and donated a very clever script to enable hashcatplus users to sort, filter and convert WPA capture files efficiently.
The script is called Script_it.sh and it runs in Backtrack.
Note that with release of hashcat and hcxtools (https://github.com/ZerBea/hcxtools) there's no more need for cleaning. Please use wlandump-ng to capture all the different kinds of WPA handshakes.