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HOST(1)                     General Commands Manual                    HOST(1)

       host - look up host names using domain server

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

       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 first decimal
       numbers  separated  by  dots,  e.g. A host name consists of
       names separated by dots, e.g.  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
       "".   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
 is a nickname for ATHOS.RUTGERS.EDU
          ATHOS.RUTGERS.EDU has address
          ATHOS.RUTGERS.EDU has address
          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 "" 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  the 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

       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
       will give a listing of all hosts in the  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
       will  give a complete download of the zone data for, 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.

       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 (8)

       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, you could
       try "host -t ns" to get a list of  all  the  name  servers  for,  and then try "host -l xxx" for all xxx on the list of
       name servers, until you find one that works.