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 information obtained from
opendirectoryd(8), including records in
/etc/networks.
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/resolv.conf
DIAGNOSTICS
Null pointer (0) returned on EOF or
error.
SEE ALSO
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.