DIG

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:

where:

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 disposal 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(@FORMAT_EXT@) for information 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 specific 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.

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 recognized:

a T_A network address

(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:

(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 option>

"-" is used to specify an option which effects the operation of dig. The following options are currently 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 successively. Lines beginning with ’;’, ’#’, or ’\n’ 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(@SYS_OPS_EXT@) command for response time comparison. This rather unelegantly makes a call to the shell. The last three lines of statistics is printed for the command:

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 variable 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 environment 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(@SYS_OPS_EXT@). If an option requires a parameter, the form is as follows:

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:

The retry and time options affect the retransmission 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

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(@LIB_NETWORK_EXT@) 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(@SYS_OPS_EXT@) 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 genesis.

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 continues with the next query.

SEE ALSO

@INDOT@named(@SYS_OPS_EXT@), resolver(@LIB_NETWORK_EXT@), resolver(@FORMAT_EXT@), nslookup(@SYS_OPS_EXT@)