DIG(1) MachTen Programmer’s Manual DIG(1)

NAME
dig - send domain name query packets to name servers

SYNOPSIS
dig [@server] domain [<query-type>] [<query-class>]
[+<query-option>] [-<dig-option>] [%comment]

DESCRIPTION
Dig (domain information groper) is a flexible command line
tool which can be used to gather information from the
Domain Name System servers. Dig has two modes: simple
interactive mode which makes a single query, and batch
which executes a query for each in a list of several query
lines. All query options are accessible from the command
line.

The usual simple use of dig will take the form:

dig @server domain query-type query-class

where:

server may be either a domain name or a dot-notation
Internet address. If this optional field is omit-
ted, dig will attempt to use the default name
server for your machine.

Note: If a domain name is specified, this will be
resolved using the domain name system resolver
(i.e., BIND). If your system does not support DNS,
you may have to specify a dot-notation address.
Alternatively, if there is a server at your dis-
posal somewhere, all that is required is that
/etc/resolv.conf be present and indicate where the
default name servers reside, so that server
itself can be resolved. See resolver(5) for infor-
mation on /etc/resolv.conf. (WARNING: Changing
/etc/resolv.conf will affect the standard resolver
library and potentially several programs which use
it.) As an option, the user may set the environment
variable LOCALRES to name a file which is to be
used instead of /etc/resolv.conf (LOCALRES is spe-
cific to the dig resolver and not referenced by
the standard resolver). If the LOCALRES variable is
not set or the file is not readable then
/etc/resolv.conf will be used.

domain is the domain name for which you are requesting
information. See OPTIONS [-x] for convenient way
to specify inverse address query.

query-type
is the type of information (DNS query type) that
you are requesting. If omitted, the default is "a"
(T_A = address). The following types are recog-
nized:

a T_A network address
any T_ANY all/any information about specified domain
mx T_MX mail exchanger for the domain
ns T_NS name servers
soa T_SOA zone of authority record
hinfo T_HINFO host information
axfr T_AXFR zone transfer
(must ask an authoritative server)
txt T_TXT arbitrary number of strings

(See RFC 1035 for the complete list.)

query-class
is the network class requested in the query. If
omitted, the default is "in" (C_IN = Internet).
The following classes are recognized:

in C_IN Internet class domain
any C_ANY all/any class information

(See RFC 1035 for the complete list.)

Note: "Any" can be used to specify a class and/or a
type of query. Dig will parse the first occurrence
of "any" to mean query-type = T_ANY. To specify
query-class = C_ANY you must either specify "any"
twice, or set query-class using "-c" option (see
below).

OTHER OPTIONS
%ignored-comment
"%" is used to included an argument that is simply
not parsed. This may be useful if running dig in
batch mode. Instead of resolving every @server-
domain-name in a list of queries, you can avoid the
overhead of doing so, and still have the domain
name on the command line as a reference. Example:

dig @128.9.0.32 %venera.isi.edu mx
isi.edu

-<dig option>
"-" is used to specify an option which effects the
operation of dig. The following options are cur-
rently available (although not guaranteed to be
useful):

-x dot-notation-address
Convenient form to specify inverse address
mapping. Instead of "dig 32.0.9.128.in-
addr.arpa" one can simply "dig -x
128.9.0.32".

-f file
File for dig batch mode. The file contains a
list of query specifications (dig command
lines) which are to be executed succes-
sively. Lines beginning with ’;’, ’#’, or
’0 are ignored. Other options may still
appear on command line, and will be in
effect for each batch query.

-T time
Time in seconds between start of successive
queries when running in batch mode. Can be
used to keep two or more batch dig commands
running roughly in sync. Default is zero.

-p port
Port number. Query a name server listening
to a non-standard port number. Default is
53.

-P[ping-string]
After query returns, execute a ping(8) com-
mand for response time comparison. This
rather unelegantly makes a call to the
shell. The last three lines of statistics is
printed for the command:

ping -s server_name 56 3

If the optional "ping string" is present, it
replaces "ping -s" in the shell command.

-t query-type
Specify type of query. May specify either an
integer value to be included in the type
field or use the abbreviated mnemonic as
discussed above (i.e., mx = T_MX).

-c query-class
Specify class of query. May specify either
an integer value to be included in the class
field or use the abbreviated mnemonic as
discussed above (i.e., in = C_IN).

-envsav
This flag specifies that the dig environment
(defaults, print options, etc.), after all
of the arguments are parsed, should be saved
to a file to become the default environment.
Useful if you do not like the standard set
of defaults and do not desire to include a
large number of options each time dig is
used. The environment consists of resolver
state variable flags, timeout, and retries
as well as the flags detailing dig output
(see below). If the shell environment vari-
able LOCALDEF is set to the name of a file,
this is where the default dig environment is
saved. If not, the file "DiG.env" is created
in the current working directory.

Note: LOCALDEF is specific to the dig
resolver, and will not affect operation of
the standard resolver library.

Each time dig is executed, it looks for
"./DiG.env" or the file specified by the
shell environment variable LOCALDEF. If such
file exists and is readable, then the envi-
ronment is restored from this file before
any arguments are parsed.

-envset
This flag only affects batch query runs.
When "-envset" is specified on a line in a
dig batch file, the dig environment after
the arguments are parsed, becomes the
default environment for the duration of the
batch file, or until the next line which
specifies "-envset".

-[no]stick
This flag only affects batch query runs. It
specifies that the dig environment (as read
initially or set by "-envset" switch) is to
be restored before each query (line) in a
dig batch file. The default "-nostick"
means that the dig environment does not
stick, hence options specified on a single
line in a dig batch file will remain in
effect for subsequent lines (i.e. they are
not restored to the "sticky" default).

+<query option>
"+" is used to specify an option to be changed in
the query packet or to change dig output specifics.
Many of these are the same parameters accepted by
nslookup(8). If an option requires a parameter,
the form is as follows:

+keyword[=value]

Most keywords can be abbreviated. Parsing of the
"+" options is very simplistic -- a value must
not be separated from its keyword by white space.
The following keywords are currently available:

Keyword Abbrev. Meaning [default]

[no]debug (deb) turn on/off debugging mode [deb]
[no]d2 turn on/off extra debugging mode [nod2]
[no]recurse (rec) use/don’t use recursive lookup [rec]
retry=# (ret) set number of retries to # [4]
time=# (ti) set timeout length to # seconds [4]
[no]ko keep open option (implies vc) [noko]
[no]vc use/don’t use virtual circuit [novc]
[no]defname (def) use/don’t use default domain name [def]
[no]search (sea) use/don’t use domain search list [sea]
domain=NAME (do) set default domain name to NAME
[no]ignore (i) ignore/don’t ignore trunc. errors [noi]
[no]primary (pr) use/don’t use primary server [nopr]
[no]aaonly (aa) authoritative query only flag [noaa]
[no]sort (sor) sort resource records [nosor]
[no]cmd echo parsed arguments [cmd]
[no]stats (st) print query statistics [st]
[no]Header (H) print basic header [H]
[no]header (he) print header flags [he]
[no]ttlid (tt) print TTLs [tt]
[no]cl print class info [nocl]
[no]qr print outgoing query [noqr]
[no]reply (rep) print reply [rep]
[no]ques (qu) print question section [qu]
[no]answer (an) print answer section [an]
[no]author (au) print authoritative section [au]
[no]addit (ad) print additional section [ad]
pfdef set to default print flags
pfmin set to minimal default print flags
pfset=# set print flags to #
(# can be hex/octal/decimal)
pfand=# bitwise and print flags with #
pfor=# bitwise or print flags with #

The retry and time options affect the retransmis-
sion strategy used by resolver library when sending
datagram queries. The algorithm is as follows:

for i = 0 to retry - 1
for j = 1 to num_servers
send_query
wait((time * (2**i)) / num_servers)
end
end

(Note: dig always uses a value of 1 for
num_servers.)

DETAILS
Dig once required a slightly modified version of the BIND
resolver(3) library. BIND’s resolver has (as of BIND 4.9)
been augmented to work properly with Dig. Essentially,
Dig is a straight-forward (albeit not pretty) effort of
parsing arguments and setting appropriate parameters. Dig
uses resolver routines res_init(), res_mkquery(),
res_send() as well as accessing _res structure.

FILES
/etc/resolv.conf initial domain name and name server
addresses

ENVIRONMENT
LOCALRES file to use in place of /etc/resolv.conf
LOCALDEF default environment file

AUTHOR
Steve Hotz hotz@isi.edu

ACKNOWLEDGMENTS
Dig uses functions from nslookup(8) authored by Andrew
Cherenson.

BUGS
Dig has a serious case of "creeping featurism" -- the
result of considering several potential uses during it’s
development. It would probably benefit from a rigorous
diet. Similarly, the print flags and granularity of the
items they specify make evident their rather ad hoc gene-
sis.

Dig does not consistently exit nicely (with appropriate
status) when a problem occurs somewhere in the resolver
(NOTE: most of the common exit cases are handled). This
is particularly annoying when running in batch mode. If
it exits abnormally (and is not caught), the entire batch
aborts; when such an event is trapped, dig simply contin-
ues with the next query.

SEE ALSO
named(8), resolver(3), resolver(5), nslookup(8)

MachTen August 30, 1990 5