This is a pure C99 program that accesses passive DNS database systems such as:

* the DNSDB API server at Farsight Security * the CIRCL pDNS server at Computer Incident Response Center (LU)

An API key is required for operation. The command syntax was inspired by a Python script called dnsdb_query, but significant departure has occurred, largely inspired by a modern understanding of "time fencing" and a desire for new features such as CSV output and JSON reprocessing.