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 for a single query, and batch mode 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 omitted, 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 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(5) for information on /etc/resolv.conf. WARNING: Changing /etc/resolv.conf will affect both 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 is not referenced by the standard resolver). If the LOCALRES variable is not set or the specified file is not readable, then /etc/resolv.conf will be used.

domain
    is the domain name for which you are requesting information. See the -x option (documented in the OTHER OPTIONS subsection of this section) 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 recognized:

    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 the -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 affects 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(8) 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:

        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. This is 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(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] 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 retransmission strategy used by the 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. As of BIND 4.9, BIND's resolver has 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(3) routines res_init(), res_mkquery(), res_send() as well as accessing the _res structure.

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

See also the explanation of the -envsav, -envset, and - [no] stick options, above.

FILES
/etc/resolv.conf
    initial domain name and name server addresses
./DiG.env
    default save file for default options

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

STANDARDS
RFC 1035.

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 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.