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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 Internet would be represented as (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 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 is set to the name of
a file, that file is searched for any 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-insensitive
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 by
searching through a list of domains until a match is found. The default
search list includes first the local domain, then its parent domains with
at least 2 name components (longest first). 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. The
search path can be changed from the default by a system-wide configuration
file (see
appeared in 4.2 BSD.
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