Name

getnetent, getnetbyaddr, getnetbyname, setnetent, endnetent − get networks entry

Syntax

#include <netdb.h>

struct netent *getnetent()

struct netent *getnetbyname(name)
char *name;

struct netent *getnetbyaddr(net, type)
long net; int type;

setnetent(stayopen)
int stayopen;

endnetent()

Description

The getnetent, getnetbyname, and getnetbyaddr subroutines each return a pointer to an object with the following structure containing the broken-out fields of a line in the networks database.

structnetent {
char*n_name;/* official name of net */
char**n_aliases;/* alias list */
intn_addrtype;/* net number type */
longn_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: AF_INET. 

n_net The network number.  Network numbers are returned in machine byte order. 

If the stayopen flag on a setnetent subroutine is NULL, the networks database is opened.  Otherwise the setnetent has the effect of rewinding the networks database. The endnetent may be called to close the networks database when processing is complete.

The getnetent subroutine simply reads the next line while getnetbyname and getnetbyaddr search until a matching name or net number is found (or until EOF is encountered).  The type must be AF_INET.  The getnetent subroutine keeps a pointer in the database, allowing successive calls to be used to search the entire file.

A call to setnetent must be made before a while loop using getnetent in order to perform initialization and an endnetent must be used after the loop.  Both getnetbyname and getnetbyaddr make calls to setnetent and endnetent.

Restrictions

All information is contained in a static area so it must be copied if it is to be saved.  Only Internet network numbers are currently understood. 

If YP is running, getnetent does not return the entries in any particular order. See the Guide to the Yellow Pages Service for setup information. 

The networks database may also be distributed via the BIND/Hesiod naming service.  See the Guide to the BIND/Hesiod Service for more information. 

Return Values

Null pointer (0) returned on EOF or error. 

Files

/etc/networks

See Also

networks(5), svc.conf(5)
Guide to the BIND/Hesiod Service
Guide to the Yellow Pages Service