getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent - get network entry
Standard C library (libc
, -lc
)
#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);
The getnetent() function reads the next entry from
the networks database and returns a netent
structure containing
the broken-out fields from the entry. A connection is opened to the
database if necessary.
The getnetbyname() function returns a
netent
structure for the entry from the database that matches
the network name
.
The getnetbyaddr() function returns a
netent
structure for the entry from the database that matches
the network number net
of type type
. The net
argument must be in host byte order.
The setnetent() function opens a connection to the
database, and sets the next entry to the first entry. If
stayopen
is nonzero, then the connection to the database will
not be closed between calls to one of the getnet*()
functions.
The endnetent() function closes the connection to the database.
The netent
structure is defined in <netdb.h>
as follows:
struct netent {
char *n_name; /* official network name */
char **n_aliases; /* alias list */
int n_addrtype; /* net address type */
uint32_t n_net; /* network number */
}
The members of the netent
structure are:
n_name
The official name of the network.
n_aliases
A NULL-terminated list of alternative names for the network.
n_addrtype
The type of the network number; always AF_INET.
n_net
The network number in host byte order.
The getnetent(), getnetbyname(),
and getnetbyaddr() functions return a pointer to a
statically allocated netent
structure, or a null pointer if an
error occurs or the end of the file is reached.
/etc/networks
networks database file
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value |
Thread safety | MT-Unsafe race:netent race:netentbuf env locale |
|
Thread safety | MT-Unsafe race:netbyname env locale |
|
Thread safety | MT-Unsafe race:netbyaddr locale |
|
Thread safety | MT-Unsafe race:netent env locale |
In the above table, netent
in race:netent
signifies
that if any of the functions setnetent(),
getnetent(), or endnetent() are used
in parallel in different threads of a program, then data races could
occur.
POSIX.1-2008.
POSIX.1-2001, 4.3BSD.
Before glibc 2.2, the net
argument of
getnetbyaddr() was of type long
.
getnetent_r(3), getprotoent(3),
getservent(3)
RFC 1101