the GNU version of look(1) does this: NAME look — display lines beginning with a given string -b Use a binary search on the given word list.

the GNU version of look(1) does this: NAME look — display lines beginning with a given string -b Use a binary search on the given word list. If you are ignoring case with -f or ignoring non-alphanumeric characters with -d, the file must be sorted in the same way. Please note that these options are the default if no filename is given. See sort(1) for more information on sorting files.