getnetent(3N)

NAME

getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), endnetent() − get network entry

SYNOPSIS

#include <sys/socket.h>
#include <netdb.h>

struct netent *getnetent(void);

struct netent *getnetbyname(const char *name);

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

int setnetent(int stayopen);

int endnetent(void);

DESCRIPTION

getnetent(), getnetbyname(), and getnetbyaddr() each return a pointer to a structure of type netent containing the broken-out fields of a line in the network data base, /etc/networks.

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; always AF_INET.

n_net The network number.

Functions behave as follows:

getnetent() Reads the next line of the file, opening the file if necessary.

setnetent() opens and rewinds the file. If the stayopen flag is non-zero, the network data base is not closed after each call to getnetent() (either directly or indirectly through one of the other getnet* calls).

endnetent() Closes the file.

getnetbyname() Sequentially searches from the beginning of the file until a network name (among either the official names or the aliases) matching its parameter name is found, or until EOF is encountered.

getnetbyaddr() Sequentially searches from the beginning of the file until a network number matching its parameter net is found, or until EOF is encountered. The parameter net must be in network order. The parameter type must be the constant AF_INET. Network numbers are supplied in host order (see byteorder(3N)).

If the system is running Network Information Service (NFS), getnetbyname() and getnetbyaddr() obtain their network information from the NIS server (see ypserv(1M) and ypfiles(4)).

RETURN VALUE

getnetent(), getnetbyname(), and getnetbyaddr() return a null pointer (0) on EOF or when they are unable to open /etc/networks. getnetbyaddr() also returns a null pointer if its type parameter is invalid.

WARNINGS

All information is contained in a static area so it must be copied if it is to be saved.

AUTHOR

getnetent() was developed by the University of California, Berkeley.

FILES

/etc/networks

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