Grepping a list of words

[John Levine]

>> Since I will have a need to run this check frequently, any suggestions for
>> a better approach are welcome.
>
>sort -u and comm(1)?

sort is O(N log N) while grep is O(N)

Which is faster depends on the constant factors in each, but as the
data sets get bigger, the log N term will dominate.  That is, for
small sets of data, I don't know which will be faster, but either will
be fast enough so who cares.  For large sets of data, the sort will be
slow.

R's,
John