GETNETENT(3) BSD Library Functions Manual GETNETENT(3)
NAME
getnetent, getnetbyaddr, getnetbyname, setnetent, endnetent -- get network entry
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <netdb.h>
struct netent *
getnetent(void);
struct netent *
getnetbyname(const char *name);
struct netent *
getnetbyaddr(uint32_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 describing an
internet network. This structure contains either the information obtained from the nameserver, named(8), broken-out fields of a line in the
network data base /etc/networks, or entries supplied by the yp(8) system. The order of the lookups is controlled by the `networks' entry in
nsswitch.conf(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 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 data base will not be closed after each call
to getnetbyname() or getnetbyaddr().
The endnetent() function closes the file.
The getnetbyname() function and getnetbyaddr() 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. The type argument must be AF_INET. Network numbers are supplied in host order.
FILES
/etc/networks
/etc/nsswitch.conf
/etc/resolv.conf
DIAGNOSTICS
Null pointer returned on EOF or error.
SEE ALSO
networks(5)
RFC 1101
HISTORY
The getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), and endnetent() functions appeared in 4.2BSD.
BUGS
The data space used by these functions is thread-specific; 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.
BSD
June 4, 1993 BSD