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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(unsigned long 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 */
unsigned long 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 encoun-
tered. The type must be AF_INET. Network numbers are supplied in host order.
FILES
/etc/networks
/etc/nsswitch.conf
/etc/resolv.conf
DIAGNOSTICS
Null pointer (0) returned on EOF or error.
SEE ALSO
networks(5)
RFC 1101
HISTORY
The getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), and endnetent() functions ap-
peared 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 net-
work numbers are currently understood. Expecting network numbers to fit in no more than 32
bits is probably naive.
BSD June 4, 1993 BSD
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