NAME

       dnsfilter - reverse-resolves IP addresses, converting them to host names.

SYNOPSIS

       dnsfilter [ opts ]

DESCRIPTION

       dnsfilter reads a series of lines from stdin, converts an IP address to a host name at the
       beginning of each line, and prints the results to stdout.

       If a line does not begin with an IP address, dnsfilter leaves the line alone.   If  an  IP
       address  does  not have a host name listed in DNS, dnsfilter leaves the line alone.  If an
       IP address has a host name listed in DNS, dnsfilter inserts an equals sign  and  the  host
       name  before  the  first  space  or  tab  in the line.  If a DNS lookup fails temporarily,
       dnsfilter inserts a colon and a dash-separated error message before the first space or tab
       in the line.

       While dnsfilter is looking up an address in DNS, it reads ahead in the input and looks for
       more addresses to look up in parallel.

OPTIONS

       opts is a series of getopt-style options:

       -c n   Do at most n DNS queries in parallel.  Default: 10.

       -l n   Read ahead at most n lines.  Default: 1000.

SEE ALSO

       dnsip(1), dnsipq(1), dnsname(1), dnsmx(1), dnstxt(1), dnsqr(1), dnsq(1), dnstrace(1)

       http://cr.yp.to/djbdns.html

                                                                                     dnsfilter(1)