adns

adns is a resolver library for C (and C++) programs, and a collection of useful DNS resolver utilities for use from the command line and in scripts:

adnslogres is a much faster version of Apache's logresolv program.
adnsresfilter is a filter which copies its input to its output, replacing IP addresses by the corresponding names, without unduly delaying the output. For example, you can usefully pipe the output of netstat -n, tcpdump -ln, and the like, into it.
adnshost is a general-purpose DNS lookup utility which can be used easily in from the command line and from shell scripts to do simple lookups. In a more advanced mode it can be used as a general-purpose DNS helper program for scripting languages which can invoke and communicate with subprocesses. See the [1]adnshost usage message for a summary of its capabilities.