refdbib is a somewhat simpler "filter"-style application. It accepts data either at stdin or from a file whose name is specified on the command line. The output always goes to stdout and can be piped to other applications or redirected into a file as you need it. For an overview of the command-line options, please see the section about starting refdbib. Keep in mind that the runbib script offers a simpler and more versatile way to run refdbib.