HOST(1M)                        TCP/IP R4.11                        HOST(1M)


NAME
       host - look up host names using domain server

SYNOPSIS
       host [-l] [-v] [-w] [-r] [-d] [-t querytype] [-a] host [ server ]

DESCRIPTION
       Host looks for information about Internet hosts.  It gets this
       information from a set of interconnected servers that are spread
       across the country.  By default, it simply converts between host
       names and Internet addresses.  However with the -t or -a options, it
       can be used to find all of the information about this host that is
       maintained by the domain server.

       The arguments can be either host names or host numbers.  The program
       first attempts to interpret them as host numbers.  If this fails, it
       will treat them as host names.  A host number consists of decimal
       numbers separated by dots (e.g., 128.6.4.194).  A host name consists
       of names separated by dots (e.g., topaz.rutgers.edu).  Unless the
       name ends in a dot, the local domain is automatically tacked on the
       end.  Thus a Rutgers user can say "host topaz", and it will actually
       look up "topaz.rutgers.edu".  If this fails, the name is tried
       unchanged (in this case, "topaz").  This same convention is used for
       mail and other network utilities.  The actual suffix to tack on the
       end is obtained by looking at the results of a "hostname" call, and
       using everything starting at the first dot.  (See below for a
       description of how to customize the host name lookup.)

       The first argument is the host name you want to look up.  If this is
       a number, an "inverse query" is done, i.e. the domain system looks in
       a separate set of databases used to convert numbers to names.

       The second argument is optional.  It allows you to specify a
       particular server to query.  If you don't specify this argument, the
       default server (normally the local machine) is used.

       If a name is specified, you may see output of three different kinds.
       Here is an example that shows all of them:
          % host sun4
          sun4.rutgers.edu is a nickname for ATHOS.RUTGERS.EDU
          ATHOS.RUTGERS.EDU has address 128.6.5.46
          ATHOS.RUTGERS.EDU has address 128.6.4.4
          ATHOS.RUTGERS.EDU mail is handled by ARAMIS.RUTGERS.EDU
       The user has typed the command "host sun4".  The first line indicates
       that the name "sun4.rutgers.edu" is actually a nickname.  The
       official host name is "ATHOS.RUTGERS.EDU'.  The next two lines show
       the address.  If a system has more than one network interface, there
       will be a separate address for each.  The last line indicates that
       ATHOS.RUTGERS.EDU does not receive its own mail.  Mail for it is
       taken by ARAMIS.RUTGERS.EDU.  There may be more than one such line,
       since some systems have more than one other system that will handle
       mail for them.  Technically, every system that can receive mail is
       supposed to have an entry of this kind.  If the system receives its
       own mail, there should be an entry that mentions the system itself;
       for example, "XXX mail is handled by XXX".  However many systems that
       receive their own mail do not bother to mention that fact.  If a
       system has a "mail is handled by" entry, but no address, this
       indicates that it is not really part of the Internet, but a system
       that is on the network will forward mail to it.  Systems on Usenet,
       Bitnet, and a number of other networks have entries of this kind.

       There are a number of options that can be used before the host name.
       Most of these options are meaningful only to the staff who have to
       maintain the domain database.

       The option -w causes host to wait forever for a response.  Normally
       it will time out after around a minute.

       The option -v causes printout to be in a "verbose" format.  This is
       the official domain master file format, which is documented in the
       man page for "named".  Without this option, output still follows this
       format in general terms, but some attempt is made to make it more
       intelligible to normal users.  Without -v, "a", "mx", and "cname"
       records are written out as "has address", "mail is handled by", and
       "is a nickname for", and TTL and class fields are not shown.

       The option -r causes recursion to be turned off in the request.  This
       means that the name server will return only data it has in its own
       database.  It will not ask other servers for more information.

       The option -d turns on debugging.  Network transactions are shown in
       detail.

       The option -t allows you to specify a particular type of information
       to be looked up.  The arguments are defined in the man page for
       "named".  Currently supported types are a, ns, md, mf, cname, soa,
       mb, mg, mr, null, wks, ptr, hinfo, minfo, mx, uinfo, uid, gid,
       unspec, and the wildcard, which may be written as either "any" or
       "*".  Types must be given in lower case.  Note that the default is to
       look first for "a", and then "mx", except that if the verbose option
       is turned on, the default is only "a".

       The option -a (for "all") is equivalent to "-v -t any".

       The option -l causes a listing of a complete domain.  E.g.
          host -l rutgers.edu
       will give a listing of all hosts in the rutgers.edu domain.  The -t
       option is used to filter what information is presented, as you would
       expect.  The default is address information, which also include PTR
       and NS records.  The command
          host -l -v -t any rutgers.edu
       will give a complete download of the zone data for rutgers.edu, in
       the official master file format.  (However the SOA record is listed
       twice, for arcane reasons.)  NOTE: -l is implemented by doing a
       complete zone transfer and then filtering out the information the you
       have asked for.  This command should be used only if it is absolutely
       necessary.

CUSTOMIZING HOST NAME LOOKUP
       In general, if the name supplied by the user does not have any dots
       in it, a default domain is appended to the end.  This domain can be
       defined in /etc/resolv.conf, but is normally derived by taking the
       local hostname after its first dot.  The user can override this, and
       specify a different default domain, using the environment variable
       LOCALDOMAIN.  In addition, the user can supply his own abbreviations
       for host names.  They should be in a file consisting of one line per
       abbreviation.  Each line contains an abbreviation, a space, and then
       the full host name.  This file must be pointed to by an environment
       variable HOSTALIASES, which is the name of the file.

SEE ALSO
       named(1M), resolver(3C), resolv.conf(4M), nslookup(1M), dnsquery(1M),
       dig(1M)

BUGS
       Unexpected effects can happen when you type a name that is not part
       of the local domain.  Please always keep in mind the fact that the
       local domain name is tacked onto the end of every name, unless it
       ends in a dot.  Only if this fails is the name used unchanged.

       The -l option only tries the first name server listed for the domain
       that you have requested.  If this server is dead, you may need to
       specify a server manually. E.g. to get a listing of foo.edu, you
       could try "host -t ns foo.edu" to get a list of all the name servers
       for foo.edu, and then try "host -l foo.edu xxx" for all xxx on the
       list of name servers, until you find one that works.


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