The s6-dnsqr program

s6-dnsqr is an analysis and debug tool. It performs a DNS resolution, then prints the contents of the answer packet, and optionally debug information during the resolution.

Interface

     s6-dnsqr [ -1 | -2 ] [ -t timeout ] [ -D level ] qtype domain

s6-dnsqr makes a recursive DNS query of type qtype for the name domain. It prints the answer packet, in human-readable form, to its standard output, then exits 0.
It does not qualify domain.
If the resolution fails for some reason, s6-dnsqr exits 2.
By default, s6-dnsqr looks for DNS cache addresses in the /etc/resolv.conf file. If the DNSCACHEIP environment variable is set and contains a list of IP (v4 or v6) addresses, separated by commas, semicolons, spaces, tabs, newlines or carriage returns, then this list is used instead.

Options

-1 : send debug information to stdout.
-2 : send debug information to stderr. This is the default. Not that those options only apply to debug output, not to the regular packet dump, which is always printed to stdout.
-t timeout : if the resolution takes more than timeout milliseconds, then it exits 99 right away with an error message. By default, timeout is 0, which means no timeout.
-D level : produce debug output during resolution. If level is:
- 0: no debug output is produced
- 1: information is printed when s6-dnsqr receives a DNS packet from a cache
- 2: information is printed before and after s6-dnsqr sends a DNS packet to a cache
- 3: both 1. and 2. apply

Notes

TXT records are printed in a quoted form similar to s6-quote's output.
If s6-dnsqr finds a record it cannot print, such as an unknown RR type, it dumps its content in the same quoted form.
The normal output format should be stable, so you can write programs that automatically parse it. However, the debug output format is undocumented and subject to change.