HOSTNAME(ADMN)                     UNIX System V



     Name
          hostname - host name resolution description


     Description
          Hostnames are domains, where a  domain  is  a  hierarchical,
          dot-separated  list  of subdomains; for example, the machine
          laiter, in the Lachman subdomain of the COM subdomain of the
          ARPANET would be represented as
                    laiter.Lachman.COM
          (with no trailing dot).

          Hostnames are often used  with  network  client  and  server
          programs,  which  must  generally  translate  the name to an
          address for use.  (This function is generally  performed  by
          the   library  routine  gethostbyname(SSC).)  Hostnames  are
          resolved by the internet  name  resolver  in  the  following
          fashion.

          If the name consists of a single component, i.e. contains no
          dot,  and if the environment variable ``HOSTALIASES'' is set
          to the name of a file, that file is searched for  an  string
          matching  the  input  hostname.   The file should consist of
          lines made up of  two  white-space  separated  strings,  the
          first  of  which  is  the  hostname alias, and the second of
          which is the complete hostname to be  substituted  for  that
          alias.   If  a  case-sensitive  match  is  found between the
          hostname to be resolved and the first field of a line in the
          file,  the  substituted  name  is  looked up with no further
          processing.

          If the input name ends with a trailing dot, the trailing dot
          is  removed,  and  the  remaining  name is looked up with no
          further processing.

          If the input name does not end with a trailing  dot,  it  is
          looked  up  in the local domain and its parent domains until
          either a match is found or fewer than 2  components  of  the
          local   domain   remain.    For   example,   in  the  domain
          CHI.Lachman.COM, the name flaime.STG will be  checked  first
          as      flaime.STG.CHI.Lachman.COM      and      then     as
          flaime.STG.Lachman.COM.  Flaime.STG.COM will not  be  tried,
          as  the there is only one component remaining from the local
          domain.


     See Also
          gethostent(SFF),resolver(ADMN), mailaddr(ADMN), named(ADMN).
          RFC883.


     (printed 8/17/89)                          HOSTNAME(ADMN)