hostname - Host name resolution description
Host names 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 follows: monet.Berkeley.EDU
Notice that there is no trailing dot.
Host names 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 gethostbyname() function.) Host names are resolved by
the Internet name resolver in the following fashion.
If the name consists of a single component (that is, contains
no dot), and if the HOSTALIASES environment variable
is set to the name of a file, that file is searched for a
string matching the input host name. The file should consist
of lines made up of two white-space separated
strings, the first of which is the host name alias, and
the second of which is the complete host name to be substituted
for that alias. If a case-insensitive 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 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 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.
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