dnsfilter(1)

📦 version 1.05, in debian bookworm, debian trixie, nixos 26.05, nixpkgs unstable, ubuntu jammy, ubuntu noble, ubuntu questing, ubuntu resolute, ubuntu stonking

💫 dnsfilter — the manual, but make it cute

okay so real talk, this is the dnsfilter(1) page from the General Commands Manual section, and she is a whole vibe. bestie, she takes IP addresses and turns them into host names. reverse DNS but make it a glow-up. let's get into it 💅

✨ NAME ✨

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

🦋 SYNOPSIS 🦋

dnsfilter [ opts ]

🌸 DESCRIPTION 🌸

okay so here's the tea 🍓 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. main character behavior, honestly.

the way that it handles each line is very "it depends", so let's break it down:

  • if a line does not begin with an IP address, dnsfilter leaves the line alone. not her business, not her problem 💅
  • if an IP address does not have a host name listed in DNS, dnsfilter also leaves the line alone. she's not gonna make something up, that's not the vibe.
  • if an IP address does have a host name listed in DNS, dnsfilter inserts an equals sign and the host name before the first space or tab in the line. slay.
  • 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. no cap, she tells you when things go sideways.

and the multitasking?? iconic. 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. she's doing seventeen things at once and still serving looks 👑

🎀 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.

like, only two options?? minimalism. she's got nothing to prove 🫶

👑 SEE ALSO 👑

these are her besties, go say hi:

and the link, exactly as written:

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

okay that's the whole page bestie, mwah 💖 this was the dnsfilter(1) manual from the djbdns family — she lives in the General Commands Manual section and she's lowkey a legend. go reverse-resolve something. periodt. ✨🦋💜

📦 where this page comes from