"extern int h_errno;

"struct hostent *gethostbyname(name)

"char *name;

"struct hostent *gethostbyaddr(addr, len, type)

"char *addr; int len, type;

"struct hostent *gethostent()

"sethostent(stayopen)

"int stayopen;

"endhostent()

struct hostent {
 char *h_name; /* official name of host */
 char **h_aliases; /* alias list */
 int h_addrtype; /* host address type */
 int h_length; /* length of address */
 char **h_addr_list; /* list of addresses from name server */
};
#define h_addr h_addr_list[0] /* address, for backward compatibility */

The members of this structure are:

\w'h_addr_list'u+2n h_name Official name of the host.

\w'h_addr_list'u+2n h_aliases A zero terminated array of alternate names for the host.

\w'h_addr_list'u+2n h_addrtype The type of address being returned; currently always AF_INET.

\w'h_addr_list'u+2n h_length The length, in bytes, of the address.

\w'h_addr_list'u+2n h_addr_list A zero terminated array of network addresses for the host. Host addresses are returned in network byte order.

\w'h_addr_list'u+2n h_addr The first address in h_addr_list; this is for backward compatiblity.

Sethostent allows a request for the use of a connected socket using TCP for queries. If the stayopen flag is non-zero, this sets the option to send all queries to the name server using TCP and to retain the connection after each call to gethostbyname or gethostbyaddr .

Endhostent closes the TCP connection.

Error return status from Gethostbyname and gethostbyaddr is indicated by return of a null pointer. The external integer h_errno may then be checked to see whether this is a temporary failure or an invalid or unknown host.

h_errno can have the following values:

Gethostent is defined, and sethostent is redefined, when libc is built to use only the routines to lookup in /etc/hosts and not the name server.

Gethostent reads the next line of /etc/hosts opening the file if necessary.

Sethostent is redefined to open and rewind the file. If stayopen flag is non-zero, the hosts data base will not be closed after each call to gethostent (either directly, or indirectly through gethostbyname or gethostbyaddr).