The s6-dnsmx program
s6-dnsmx finds the MX information associated to a domain name.
s6-dnsmx [ -q ] [ -r ] [ -t timeout ] domain
- s6-dnsmx makes an MX query for the name domain. It
waits for the result and prints the obtained information, one exchanger
per line, then exits 0. It prints the preference, then a space, then
the exchanger name.
- If the domain exists but no relevant field has been found, it exits 1.
- If the DNS answered but no answer is available, it prints a relevant
error message and exits 2.
- By default, s6-dnsmx 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.
- -q : qualify. Qualifies domain before resolution,
according to suffixes found in /etc/resolv.conf. If the DNSQUALIFY
environment variable is set and contains a list of suffixes separated by spaces,
tabs, newlines or carriage returns, then this list is used instead. By
default, no qualification is used: if domain is not a FQDN, a dot
is just appended to it.
- -r : random. By default, the program does not sort the
result, but prints them in the order received from the DNS. With this
option, it performs a random permutation on the results before printing
- -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.