I had no trouble opening com.apple.safari.searchhelper.binarycookies with BBEdit. The content of the file is obviously binary, but there was enough ascii text to determine the content of the file contains Cookie data from a shopping cart I just visited.
cook�����
<snip — a lot of unreadable gobbledygook where BBEdit is attempting to make sense out of non-printing binary text.>
¿A.www.rockler.com�frontend�/�8daf27gcunvbilqma2qjnveb82�\��������������8���I���X���Z��������������ÇY ¿A���¬∞
¿A.www.rockler.com�sli_cart_items�/�0�_��������������8���I���X���Z��������������ÇY ¿A���¬∞
¿A.www.rockler.com�sli_cart_value�/�0.00����������º�������®���������������8���A���E���G�������������Ä‘cI—A�,
<snip — a few hundred (thousand?) more gobbledygook characters.>
If you really want to read this file and understand hexadecimal encoding of binary.
iHex,
Hex-Editor,
Hex Edit Pro, and
Hex are all available on the App Store at prices ranging from free to $6.99.
For details on how this file is used in Safari, you are going to have to have a long chat with Apple's Safari development team. As far as deleting it, I am confident it will be recreated the next time you launch Safari.
