Host Names – hostent

An Internet host-name-to-address mapping is represented by the hostent structure as defined in gethostent(3C):

struct hostent {
    char  *h_name;            /* official name of host */
    char  **h_aliases;        /* alias list */
    int   h_addrtype;         /* hostaddrtype(e.g.,AF_INET6) */
    int   h_length;           /* length of address */
    char  **h_addr_list;      /* list of addrs, null terminated */
};
/*1st addr, net byte order*/
#define h_addr h_addr_list[0]

getipnodebyname(3C)

Maps an Internet host name to a hostent structure

getipnodebyaddr(3C)

Maps an Internet host address to a hostent structure

freehostent(3C)

Frees the memory of a hostent structure

inet_ntop(3C)

Maps an Internet host address to a string

The routines return a hostent structure that contains the name of the host, its aliases, the address type, and a NULL-terminated list of variable length addresses. The list of addresses is required because a host can have many addresses. The h_addr definition is for backward compatibility, and is the first address in the list of addresses in the hostent structure.