getnetent, getnetbyaddr, getnetbyname, setnetent, endnetent
Purpose
Gets network entry.
Library
Sockets Library (libsock.a)
Syntax
#include <netdb.h>
struct netent *getnetent ( ) void setnetent (stayopen)
int stayopen;
struct netent *getnetbyname (name)
char *name; void endnetent ( )
struct netent *getnetbyaddr (net, type)
long net;
int type;
Description
The getnetent, getnetbyname, and getnetbyaddr subroutines
each return a pointer to an object. This object is a
netent structure, which contains the field of a line in
the /etc/networks file (the network data base). The
netent structure is defined in the netdb.h header file,
and it contains the following members:
char *n_name; /* official name of net */
char **n_aliases; /* alias list */
int n_addrtype; /* net number type */
long n_net; /* net number */
The members of the structure are defined below:
n_name Official name of the network.
n_aliases An array, terminated with a 0, of alternate
names for the network.
n_addrtype The type of network number being returned.
AF_INET is the only valid value for this
field.
n_net The network number. Network numbers are
returned in machine byte order.
The getnetent subroutine reads the next line of the file.
If the file is not open, getnetent opens it.
The setnetent subroutine opens and rewinds the file. If
the stayopen parameter is 0, the net data base is closed
after each call to getnetent. Otherwise, the file is not
closed after each call.
The endnetent subroutine closes the file.
The net parameter of getnetbyaddr subroutine contains the
number of the network to be located. The type parameter
specifies the address family for the network. The only
supported value is AF_INET.
The getnetbyname and getnetbyaddr subroutines search the
file sequentially from its beginning until:
o finding a matching net name, for getnetbyname,
o finding a matching net number and type, for
getnetbyaddr, or
o encountering the end of the file, for either routine.
Network numbers are supplied in host order.
Return Value
A pointer to a netent structure is returned on success.
Note: The return value points to static data that is
overwritten by subsequent calls.
A NULL pointer (0) is returned if an error occurs or the
end of the file is reached.
File
/etc/networks Network name data base.
Related Information
The discussion of /etc/networks in Interface Program for
use with TCP/IP.