lookbib prints a prompt on the standard error (unless the standard input
is not a terminal), 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 indxbib(1) exists, then it will be searched instead; each index can
cover multiple databases.