hostname(ADMN)                  19 June 1992                  hostname(ADMN)


 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 bigbooty, in the Yoyodyne
    subdomain of the COM subdomain of the Internet would be represented as

       bigbooty.Yoyodyne.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(SLIB).)
    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 in a 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 Sj.Yoyodyne.COM, the name yaya.Eng will be checked first as
    yaya.Eng.Sj.Yoyodyne.COM and then as yaya.Eng.Yoyodyne.COM.  Yaya.Eng.COM
    will not be tried, as the there is only one component remaining from the
    local domain.

 See also

    gethostbyname(SLIB), resolver(SFF), mailaddr(ADMN), named(ADMN) RFC1035.