How to query macOS DNS resolver from Terminal?
I know how to query DNS using tools like dig, host, etc. But their macOS man pages state:
The results of DNS queries may also differ from queries that use the macOS DNS routing library.
Given that, how do I query DNS in terminal and get the same results as native macOS apps?
When testing DNS changes I sometimes see different results between the unix tools and native mac applications. Here is an example of what I've encountered:
$ dig +short example.com
192.168.0.100
dig shows that the DNS query returns a local address handled by our own DNS server. Meanwhile using the macOS 'Network Utility' lookup returns a cached result:
using the macOS network reachability tool, I get a cached result as well (for those not familiar with the output the IP address is revealed in the last line):
$ scutil -W -r example.com
0: direct
<SCNetworkReachability 0x7f8a39605ab0 [0x7fffa3c088f0]> {name = example.com}
Reachable
1: start
<SCNetworkReachability 0x7f8a39606000 [0x7fffa3c088f0]> {name = example.com}
2: on runloop
<SCNetworkReachability 0x7f8a39606000 [0x7fffa3c088f0]> {name = example.com (DNS query active), flags = 0x00000002, if_index = 13}
Reachable
*** 13:08:23.373
3: callback w/flags=0x00000002 (info="by name")
<SCNetworkReachability 0x7f8a39606000 [0x7fffa3c088f0]> {name = example.com (complete, 93.184.216.34, 2606:2800:220:1:248:1893:25c8:1946), flags = 0x00000002, if_index = 13}
Reachable
Is there a macOS command line utility to resolve addresses using the same heuristic that native mac apps use? Note: I am not interested in clearing the DNS cache, I'm interested in using the native macOS DNS resolver from a script. I've looked at man pages for mDNSResponder, dns-sd, scutil, networksetup, and dscacheutil none of which seem to query dns.
Josh2 Answers
It seems taking the effort to formulate the question I understood the problem better to perform more precise google searches and found the answer.
On macOS querying DNS is achieved by:
$ dscacheutil -q host -a name example.com
name: example.com
ipv6_address: 2606:2800:220:1:248:1893:25c8:1946
name: example.com
ip_address: 93.184.216.34
Like most macOS shell commands it is not quite as nice as the unix equivalent, but it gives me consistent results with native mac apps.
I found this from https://random.ac/cess/2018/04/12/macos-dig-vs-dscacheutil-while-using-split-dns-with-viscosity-vpn-client/
JoshIn addition to the great dig (pun intended) of the dscacheutil usage that's not covered by the man documentation, I'd like to add that at the core of the macOs name resolution system sits the mDNSresponder service, and it seems to be gathering all different sources of the lookup information under the common interface.
The tool for interacting with the mDNS subsystem is dns-sd, and as such, there is another way of querying for the DNS records that will honor all available resolvers:
~ » dns-sd -G v4v6 google.com
DATE: ---Wed 04 Nov 2020---
19:05:47.081 ...STARTING...
Timestamp A/R Flags if Hostname Address TTL
19:05:47.175 Add 2 0 google.com. 2A00:1450:4001:081D:0000:0000:0000:200E%<0> 377
19:05:47.255 Add 2 0 google.com. 172.217.22.110 377
or
~ » dns-sd -q google.com
DATE: ---Wed 04 Nov 2020---
20:27:50.834 ...STARTING...
Timestamp A/R Flags if Name Type Class Rdata
20:27:50.925 Add 2 0 google.com. Addr IN 172.217.22.110
or even
~ » dns-sd -q google.com TXT
DATE: ---Wed 04 Nov 2020---
20:30:45.908 ...STARTING...
Timestamp A/R Flags if Name Type Class Rdata
20:30:48.831 Add 3 0 google.com. TXT IN 36 bytes: 23 76 3D 73 70 66 31 20 69 6E 63 6C 75 64 65 3A 5F 73 70 66 2E 67 6F 6F 67 6C 65 2E 63 6F 6D 20 7E 61 6C 6C
20:30:48.831 Add 3 0 google.com. TXT IN 46 bytes: 2D 64 6F 63 75 73 69 67 6E 3D 30 35 39 35 38 34 38 38 2D 34 37 35 32 2D 34 65 66 32 2D 39 35 65 62 2D 61 61 37 62 61 38 61 33 62 64 30 65
20:30:48.831 Add 3 0 google.com. TXT IN 46 bytes: 2D 64 6F 63 75 73 69 67 6E 3D 31 62 30 61 36 37 35 34 2D 34 39 62 31 2D 34 64 62 35 2D 38 35 34 30 2D 64 32 63 31 32 36 36 34 62 32 38 39
20:30:48.831 Add 3 0 google.com. TXT IN 60 bytes: 3B 66 61 63 65 62 6F 6F 6B 2D 64 6F 6D 61 69 6E 2D 76 65 72 69 66 69 63 61 74 69 6F 6E 3D 32 32 72 6D 35 35 31 63 75 34 6B 30 61 62 30 62 78 73 77 35 33 36 74 6C 64 73 34 68 39 35
20:30:48.831 Add 2 0 google.com. TXT IN 65 bytes: 40 67 6C 6F 62 61 6C 73 69 67 6E 2D 73 6D 69 6D 65 2D 64 76 3D 43 44 59 58 2B 58 46 48 55 77 32 77 6D 6C 36 2F 47 62 38 2B 35 39 42 73 48 33 31 4B 7A 55 72 36 63 31 6C 32 42 50 76 71 4B 58 38 3D
Truth to be told, this is not the best command for scripting as it operates in an interactive continuous monitoring mode that would notify of any changes on the given address until one interrupts it. Although it allows for some fun stuff like watching a VPN-only path to disappear and then reappear when you reconnect:
~ » dns-sd -G v4v6 vpn.only.address.com
DATE: ---Wed 04 Nov 2020---
19:10:01.672 ...STARTING...
Timestamp A/R Flags if Hostname Address TTL
19:10:01.673 Add 40000002 0 vpn.only.address.com. 10.100.100.100 333
19:10:01.759 Add 2 0 vpn.only.address.com. 0000:0000:0000:0000:0000:0000:0000:0000%<0> 323 No Such Record
19:10:07.703 Rmv 0 0 vpn.only.address.com. 10.100.100.100 0
19:10:10.783 Add 2 0 vpn.only.address.com. 0.0.0.0 4502 No Such Record
19:10:10.905 Add 2 0 vpn.only.address.com. 0000:0000:0000:0000:0000:0000:0000:0000%<0> 4502 No Such Record
19:10:32.669 Add 3 0 vpn.only.address.com. 10.100.100.100 298
19:10:32.670 Add 2 0 vpn.only.address.com. 0000:0000:0000:0000:0000:0000:0000:0000%<0> 228 No Such Record
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