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HOST(1)                BSD Reference Manual               HOST(1)


NAME
       rhost - look up host names using domain server

SYNOPSIS
       rhost  [-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 con-
       verts  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 num-
       bers.  If this fails, it will treat them as host names.  A
       host number consists of first decimal numbers separated by
       dots, e.g. 128.6.4.194 A host name consists of names sepa-
       rated  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  utili-
       ties.  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  dif-
       ferent 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



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HOST(1)                BSD Reference Manual               HOST(1)


       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 indi-
       cates 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  sup-
       posed  to  have  an  entry  of  this  kind.  If the system
       receives its own mail, there should be an entry  the  men-
       tions  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 wild-
       card, which may be written as either "any" or "*".   Types



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HOST(1)                BSD Reference Manual               HOST(1)


       must  be given in lower case.  Note that the default is to
       look first for "a", and then "mx", except that if the ver-
       bose 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  rut-
       gers.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 dif-
       ferent  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  con-
       tains  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)

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



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HOST(1)                BSD Reference Manual               HOST(1)


       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.




















































4.4BSD                                                          4