27.18 Fast Searches and Spelling Checks with "look"

Every so often, someone has designed a new, faster grep-type program. Public domain software archives have more than a few of them. One of the fastest search programs has been around for years: look. It uses a binary search method that's very fast. But look won't solve all your problems: it works only on files that have been sorted (36.1). If you have a big file or database that can be sorted, searching it with look will save a lot of time. For example, to search for all lines that start with Alpha:

% look Alpha filename
Alpha particle
Alphanumeric