NAME
getnetent,
getnetbyaddr,
getnetbyname,
setnetent,
endnetent —
get network entry
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <netdb.h>
struct netent *
getnetent();
struct netent *
getnetbyname(
const
char *name);
struct netent *
getnetbyaddr(
uint32_t
net,
int type);
setnetent(
int
stayopen);
endnetent();
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 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 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. Network numbers are supplied in
host order.
FILES
- /etc/networks
-
DIAGNOSTICS
Null pointer (0) returned on
EOF
or error.
SEE ALSO
networks(5),
nsswitch.conf(5)
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 probably
naive.