GETNETENT(3)

NAME
getnetent, getnetbyaddr, getnetbyname, setnetent, endnetent - get network entry

SYNOPSIS
#include <netdb.h>
struct netent *
getnetent(void);
struct netent *
getnetbyname(const char *name);
struct netent *
getnetbyaddr(in_addr_t net, int type);
void
setnetent(int stayopen);
void
endnetent(void);

DESCRIPTION
The getnetent(), 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 database, /etc/networks.

    struct	netent {
    	char		*n_name;	/* official name of net */
    	char		**n_aliases;	/* alias list */
    	int		n_addrtype;	/* net number type */
    	in_addr_t	n_net;		/* net number */
    };

The members of this structure are:

n_name
    The official name of the network.

n_aliases
    A null-terminated list of alternate 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 machine byte order.

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

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

The endnetent() function closes the file.

The getnetbyname() and getnetbyaddr() functions search the domain name server if the system is configured to use one. If the search fails, or no name server is configured, they 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 order.

RETURN VALUES
The getnetent(), getnetbyaddr(), and getnetbyname() functions return NULL if the requested entry is not found.

FILES
/etc/networks

SEE ALSO
resolver(3), networks(5)

STANDARDS
These functions conform to p1003.1-2008.

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

BUGS
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 naive.