dnsfilter(1)                         General Commands Manual                         dnsfilter(1)



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, dns‐
       filter 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)