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NAME

       gethostbyname, gethostbyaddr, herror, hstrerror - get network host entry

SYNOPSIS

       #include <network.h>

       struct hostent *gethostbyname(const char *name);

       struct hostent *gethostbyaddr(const char *addr, int len, int type);

       void herror(const char *s);

       const char * hstrerror(int err);

DESCRIPTION

       The gethostbyname() function returns a structure  of  type

       hostent  for  the  given host name.  Here name is either a

       host name, or an IPv4 address in standard dot notation, or

       an IPv6 address in colon (and possibly dot) notation. (See

       RFC 1884 for the description of IPv6 addresses.)  If  name

       is  an  IPv4  or  IPv6 address, no lookup is performed and

       gethostbyname() simply copies name into the  h_name  field

       and  its struct in_addr equivalent into the h_addr_list[0]

       field of the returned hostent structure.  If name  doesn't

       end  in  a dot and the environment variable HOSTALIASES is

       set, the alias file pointed to by HOSTALIASES  will  first

       be  searched for name.  (See hostname(7) for the file for­

       mat.)  The current domain and  its  parents  are  searched

       unless name ends in a dot.

       The  gethostbyaddr()  function returns a structure of type

       hostent for the given host address addr of length len  and

       address  type  type.   The only valid address type is cur­

       rently AF_INET.

       The  (obsolete) herror() function prints the error message

       associated with the current value of h_errno on stderr.

       The (obsolete) hstrerror() function takes an error  number

       (typically  h_errno) and returns the corresponding message

       string.

       The domain name queries carried out by gethostbyname() and

       gethostbyaddr()  use  a  combination  of any or all of the

       name server named(8), a broken out line  from  /etc/hosts,

       and the Network Information Service (NIS or YP), depending

       upon the contents of the  order  line  in  /etc/host.conf.

       (See   resolv+(8)).    The  default  action  is  to  query

       named(8), followed by /etc/hosts.

       The hostent structure is defined in <netdb.h> as follows:

              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 */

              }

              #define h_addr  h_addr_list[0]  /* for backward compatibility */

       The members of the hostent structure are:

       h_name The official name of the host.

       h_aliases

              A zero-terminated array of  alternative  names  for

              the host.

       h_addrtype

              The type of address; always AF_INET at present.

       h_length

              The length of the address in bytes.

       h_addr_list

              A  zero-terminated  array  of network addresses for

              the host in network byte order.

       h_addr The first address in h_addr_list for backward  com­

              patibility.

RETURN VALUE

       The  gethostbyname()  and gethostbyaddr() functions return

       the hostent structure  or  a  NULL  pointer  if  an  error

       occurs.   On  error,  the  h_errno variable holds an error

       number.

ERRORS

       The variable h_errno can have the following values:

       HOST_NOT_FOUND

              The specified host is unknown.

       NO_ADDRESS or NO_DATA

              The requested name is valid but does not have an IP

              address.

       NO_RECOVERY

              A non-recoverable name server error occurred.

       TRY_AGAIN

              A temporary error occurred on an authoritative name

              server.  Try again later.