lookbib prints a prompt on the standard error (unless the standard input is not
reads from the standard input a line containing a set of keywords,
searches the bibliographic databases
filename... for references containing those keywords,
prints any references found on the standard output,
and repeats this process until the end of input.
For each database
filename to be searched,
if an index
filename.i created by
exists, then it will be searched instead;
each index can cover multiple databases.