Many systems come with a database that records a list of networks known
to the system developer. This is usually kept either in the file
`/etc/networks' or in an equivalent from a name server. This data
base is useful for routing programs such as
route, but it is not
useful for programs that simply communicate over the network. We
provide functions to access this data base, which are declared in
AF_INETfor Internet networks.
unsigned long int n_net
getnetbyaddr functions to search
the networks database for information about a specific network. The
information is returned in a statically-allocated structure; you must
copy the information if you need to save it.
getnetbynamefunction returns information about the network named name. It returns a null pointer if there is no such network.
getnetbyaddrfunction returns information about the network of type type with number net. You should specify a value of
AF_INETfor the type argument for Internet networks.
getnetbyaddr returns a null pointer if there is no such
You can also scan the networks database using
endnetent. Be careful in using these
functions, because they are not reentrant.
If the stayopen argument is nonzero, this sets a flag so that
subsequent calls to
not close the database (as they usually would). This makes for more
efficiency if you call those functions several times, by avoiding
reopening the database for each call.
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