View source for Dig (command)

{{Short description|Network administration command-line tool}}
{{refimprove|date=April 2011}}
{{lowercase}}
{{Infobox software 
| name                    = dig
| logo                   = 
| screenshot             = DiG 9.18.1 screenshot.png
| screenshot size        = 
| caption                = 
| author                 = Steve Hotz, Michael Sawyer
| developer              = [[Internet Systems Consortium]] (originally [[Computer Systems Research Group]])
| operating system       = [[Linux]], [[NetBSD]], [[FreeBSD]], [[OpenBSD]], [[macOS]], [[Microsoft Windows|Windows]], [[Solaris (operating system)|Solaris]], [[illumos]], [[OpenVMS]]
| genre                  = DNS lookup tool
| license                = [[Mozilla Public License]] ([[ISC license]] before 9.11<ref>{{cite web|url=https://gitlab.isc.org/isc-projects/bind9/blob/v9_11/LICENSE|title=LICENSE in Bind 9.11 branch|access-date=2021-09-19|archive-date=2021-08-22|archive-url=https://web.archive.org/web/20210822235017/https://gitlab.isc.org/isc-projects/bind9/blob/v9_11/LICENSE|url-status=dead}}</ref>)
| website                = https://www.isc.org/bind/
}}

'''dig''' is a [[network administration]] [[command-line tool]] for querying the [[Domain Name System]] (DNS).

dig is useful for network troubleshooting and for educational purposes.<ref name="linuxize">{{Cite web |date=2020-02-26 |title=Dig Command in Linux (DNS Lookup) |url=https://linuxize.com/post/how-to-use-dig-command-to-query-dns-in-linux/ |access-date=2024-03-07 |website=linuxize.com}}</ref> It can operate based on command line option and flag arguments, or in batch mode by reading requests from an operating system file. When a specific [[name server]] is not specified in the command invocation, it uses the operating system's default resolver, usually configured in the file [[resolv.conf]]. Without any arguments it queries the [[DNS root zone]].

dig supports [[Internationalized domain name]] (IDN) queries.

dig is a component of the domain name server software suite [[BIND]]. dig supersedes in functionality older tools, such as [[nslookup]] and the program [[host (Unix)|host]]; however, the older tools are still used in complementary fashion.

== Example usage ==

=== Basic ===
In this example, dig is used to query for '''''any''''' type of record information in the domain ''example.com'':

<syntaxhighlight lang="zone" highlight="1" style="font-size:8pt;">
$ dig example.com any
; <<>> DiG 9.6.1 <<>> example.com any
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4016
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;example.com.                   IN      ANY

;; ANSWER SECTION:
example.com.            172719  IN      NS      a.iana-servers.net.
example.com.            172719  IN      NS      b.iana-servers.net.
example.com.            172719  IN      A       208.77.188.166
example.com.            172719  IN      SOA     dns1.icann.org. hostmaster.icann.org. 2007051703 7200 3600 1209600 86400

;; Query time: 1 msec
;; SERVER: ::1#53(::1)
;; WHEN: Wed Aug 12 11:40:43 2009
;; MSG SIZE  rcvd: 154
</syntaxhighlight>

The number '''''172719''''' in the above example is the [[Time to live#DNS records|time to live]] value, which indicates the time of validity of the data.

The '''''any''''' DNS query is a special meta query which is now deprecated. Since [https://datatracker.ietf.org/doc/html/rfc8482 around 2019], most public DNS servers have stopped answering most DNS '''''ANY''''' queries usefully [https://blog.cloudflare.com/rfc8482-saying-goodbye-to-any/].

If '''''ANY''''' queries do not enumerate multiple records, the only option is to request each [[List of DNS record types|record type]] (e.g. A, CNAME, or MX) individually.

=== Specific DNS server ===
Queries may be directed to designated DNS servers for specific records; in this example, [[MX record]]s:
<syntaxhighlight lang="zone" highlight="1" style="font-size:8pt;">
$ dig wikimedia.org MX @ns0.wikimedia.org
; <<>> DiG 9.11.3 <<>> wikimedia.org MX @ns0.wikimedia.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39041
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1024
; COOKIE: c9735311d2d2fa6e3b334ab01b67960d (good)
;; QUESTION SECTION:
;wikimedia.org.                 IN      MX

;; ANSWER SECTION:
wikimedia.org.          3600    IN      MX      10 mx1001.wikimedia.org.
wikimedia.org.          3600    IN      MX      50 mx2001.wikimedia.org.

;; Query time: 1 msec
;; SERVER: 208.80.154.238#53(208.80.154.238)
;; WHEN: Sat Sep 18 21:33:24 PDT 2021
;; MSG SIZE  rcvd: 108
</syntaxhighlight>

=== With output formatting ===
There are many [https://downloads.isc.org/isc/bind9/cur/9.19/doc/arm/html/manpages.html#dig-dns-lookup-utility output formatting options] available. A common selection to make the output more terse is:

<syntaxhighlight lang="zone" highlight="1" style="font-size:8pt;">
$ dig +noall +answer +multiline wikimedia.org MX
wikimedia.org.          3600 IN MX 10 mx1001.wikimedia.org.
wikimedia.org.          3600 IN MX 50 mx2001.wikimedia.org.
</syntaxhighlight>

Where '''''+noall +answer +multiline''''' are simply output formatting flags.

==History==

dig was originally written by Steve Hotz and incorporated into [[BIND]] 4 since at least 1990;<ref name=hotz>{{cite web |title=dig (4.4BSD of 1990) |url=https://man.freebsd.org/cgi/man.cgi?query=dig&apropos=0&sektion=0&manpath=4.4BSD+Lite2&arch=default&format=html |website=man.freebsd.org |access-date=2024-05-17}}</ref> later it was rewritten by Michael Sawyer, and is maintained by the [[Internet Systems Consortium]] as part of BIND 9.

When originally written, the manual page for dig indicated that its name was an acronym for "Domain Information Groper".{{r|hotz}} This expansion was removed in 2017; the tool's name is now simply "dig".

==See also==
* [[BIND]] name server
* [[Root name server]] – top-level name servers providing top level domain name resolution
* [[List of DNS record types]] – possible types of records stored and queried within DNS
* [[whois]]
* [[Host (Unix)|host]] is a simple utility for performing Domain Name System lookups
* [[nslookup]], another utility that can be used to obtain similar information

==References==
{{Reflist}}

===Bibliography===
* Paul Albitz and Cricket Liu. DNS and BIND, 5th Edition. Nutshell Series. O'Reilly and Associates, Inc., 2006.

==External links==
*[https://downloads.isc.org/isc/bind9/cur/9.19/doc/arm/html/manpages.html#dig-dns-lookup-utility Official BIND 9 man page for dig]
*[https://www.madboa.com/geek/dig/ How to use dig to query DNS name servers]
*[https://gitlab.isc.org/isc-projects/bind9/-/tree/main/bin/dig Dig source code in ISC Gitlab repository]

{{Unix commands}}

[[Category:DNS software]]
[[Category:Domain Name System]]
[[Category:Free network-related software]]