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GETNETENT(3) Library Functions Manual GETNETENT(3)

getnetent, getnetbyaddr, getnetbyname, setnetent, endnetent — get network entry

library “libc”

#include <netdb.h>

struct netent *
getnetent();

struct netent *
getnetbyname(const char *name);

struct netent *
getnetbyaddr(uint32_t net, int type);

void
setnetent(int stayopen);

void
endnetent(void);

The (), getnetbyname(), and getnetbyaddr() functions each return a pointer to an object with the following structure containing the broken-out fields of a line in the network data base as described in networks(5). 
struct	netent {
	char		*n_name;	/* official name of net */
	char		**n_aliases;	/* alias list */
	int		n_addrtype;	/* net number type */
	uint32_t	n_net;		/* net number */
};

The members of this structure are:

n_name
The official name of the network.
n_aliases
A zero terminated list of alternative names for the network.
n_addrtype
The type of the network number returned; currently only AF_INET.
n_net
The network number. Network numbers are returned in host byte order.

The () function reads the next line of the file, opening the file if necessary.

The () function opens and rewinds the file. If the stayopen flag is non-zero, the net data base will not be closed after each call to getnetbyname() or getnetbyaddr().

The () function closes the file.

The () and () functions sequentially search from the beginning of the file until a matching net name or net address and type is found, or until EOF is encountered. Network numbers are supplied in host byte order.

/etc/networks
 

Null pointer (NULL) returned on EOF or error.

networks(5), nsswitch.conf(5)

The getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), and endnetent() functions appeared in 4.2BSD.

The data space used by these functions is static; if future use requires the data, it should be copied before any subsequent calls to these functions overwrite it. Only Internet network numbers are currently understood. Expecting network numbers to fit in no more than 32 bits is probably naive.

February 21, 2018 NetBSD-9.2