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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)