HOSTNAME(7)	    UNIX Programmer's Manual	      HOSTNAME(7)



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
     monet, in the Berkeley subdomain of the EDU subdomain of the
     ARPANET would be represented as
	       monet.Berkeley.EDU
     (with no trailing dot).

     Hostnames are often used with network client and server pro-
     grams, which must generally translate the name to an address
     for use.  (This function is generally performed by the
     library routine _g_e_t_h_o_s_t_b_y_n_a_m_e(3).) 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 host-
     name to be resolved and the first field of a line in the
     file, the substituted name is looked up with no further pro-
     cessing.

     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
     CS.Berkeley.EDU, the name lithium.CChem will be checked
     first as lithium.CChem.CS.Berkeley.EDU and then as
     lithium.CChem.Berkeley.EDU.  Lithium.CChem.EDU will not be
     tried, as the there is only one component remaining from the
     local domain.

SEE ALSO
     gethostbyname(3), resolver(5), mailaddr(7), named(8), RFC883










Printed 11/26/99	November 21, 1987			1