gethostent, gethostbyname, and gethostbyaddr() each return a pointer to an object with the following structure containing the broken-out fields of a line in the network host data base, /etc/hosts. In the case of gethostbyaddr(), addr is a pointer to the binary format address of length len (not a character string).

struct hostent {

char *h_name; /* official name of host */

char **h_aliases; /* alias list */

int h_addrtype; /* address type */

int h_length; /* length of address */

char **h_addr_list; /* list of addresses from name server */ };

The members of this structure are:

h_name

Official name of the host.

h_aliases

A zero terminated array of alternate names for the host.

h_addrtype

The type of address being returned; currently always AF_INET.

h_length

The length, in bytes, of the address.

h_addr_list

A pointer to a list of network addresses for the named host. Host addresses are returned in network byte order.

gethostent() reads the next line of the file, opening the file if necessary.

sethostent() opens and rewinds the file. If the stayopen flag is non-zero, the host data base will not be closed after each call to gethostent() (either directly, or indirectly through one of the other (gethost) calls).

endhostent() closes the file.

gethostbyname() and gethostbyaddr() sequentially search from the beginning of the file until a matching host name or host address is found, or until end-of-file is encountered. Host addresses are supplied in network order.

/etc/hosts