getipnodebyname(e)  Linux Programmer's Manual  getipnodebyname(e)



NAME
       getipnodebyname,  getipnodebyaddr,  freehostent - get net-
       work host names and addresses

SYNOPSIS
       #include <sys/types.h>
       #include <sys/socket.h>
       #include <netdb.h>

       struct hostent *getipnodebyname(const char *name,
                                int af, int flags,
                                int *error_num);

       struct hostent *getipnodebyaddr(const void *addr,
                                size_t len, int af,
                                int *error_num);

       void freehostent(struct hostent *ip);

DESCRIPTION
       The getipnodebyname(e)  and  getipnodebyaddr(r)  functions
       return  the  names and addresses of a network host.  These
       functions return a pointer to the following structure:

       struct hostent {
               char    *h_name;
               char    **h_aliases;
               int     h_addrtype;
               int     h_length;
               char    **h_addr_list;
       };

       These functions replace the gethostbyname(e) and  gethost-
       byaddr(r) functions, which could only access the IPv4 net-
       work address family.  The getipnodebyname(e)  and  getipn-
       odebyaddr(r) functions can access multiple network address
       families.

       Unlike the gethostby  functions,  these  functions  return
       pointers  to  dynamically  allocated memory.  The freehos-
       tent(t) function is used to release the dynamically  allo-
       cated  memory after the caller no longer needs the hostent
       structure.

   getipnodebyname parameters
       The getipnodebyname(e) function looks up network addresses
       for  the  host  specified  by  the name parameter.  The af
       parameter specifies one of the following values:

       AF_INET
              The name parameter points  to  a  dotted-quad  IPv4
              address or a name of an IPv4 network host.

       AF_INET6
              The  name  parameter  points  to a hexadecimal IPv6
              address or a name of an IPv6 network host.

       The flags parameter specifies  additional  options.   More
       than  one option can be specified by logically OR-ing them
       together.  flags should be set to  0  if  no  options  are
       desired.

       AI_V4MAPPED
              This  flag is used with AF_INET6 to request a query
              for IPv4 addresses instead of IPv6  addresses;  the
              IPv4 addresses will be mapped to IPv6 addresses.

       AI_ALL This  flag  is  used  with AI_V4MAPPED to request a
              query for both IPv4 and IPv6 addresses.   Any  IPv4
              address found will be mapped to an IPv6 address.

       AI_ADDRCONFIG
              This  flag is used with AF_INET6 to further request
              that queries for IPv6 addresses should not be  made
              unless  the  system  has  at least one IPv6 address
              assigned to a network interface, and  that  queries
              for  IPv4  addresses  should not be made unless the
              system has at least one IPv4 address assigned to  a
              network interface.  This flag may be used by itself
              or with the AI_V4MAPPED flag.

       AI_ALL This  flag  is  equivalent  to   (AI_ADDRCONFIG   |
              AI_V4MAPPED).

   getipnodebyaddr parameters
       The  getipnodebyaddr(r)  function looks up the name of the
       host whose network address is specified by the addr param-
       eter.   The  af  parameter  specifies one of the following
       values:

       AF_INET
              The addr parameter points to a struct  in_addr  and
              len must be set to sizeof(struct in_addr).

       AF_INET6
              The  addr parameter points to a struct in6_addr and
              len must be set to sizeof(struct in6_addr).

RETURN VALUE
       A null pointer is  returned  if  an  error  occurred,  and
       error_num  will  contain  an error code from the following
       list:

       HOST_NOT_FOUND
              The host name or network address was not found.

       NO_ADDRESS
              The  domain  name  server  recognized  the  network
              address  or name, but no answer was returned.  This
              can happen  if  the  network  host  has  only  IPv4
              addresses  and  a  request  has  been made for IPv6
              information only, or vice versa.

       NO_RECOVERY
              The domain name server returned a permanent failure
              response.

       TRY_AGAIN
              The domain name server returned a temporary failure
              response.  You might have better luck next time.

       A successful query returns a pointer to a  hostent  struc-
       ture that contains the following fields:

       h_name This is the official name of this network host.

       h_aliases
              This  is an array of pointers to unofficial aliases
              for the same host.  The array is  terminated  by  a
              null pointer.

       h_addrtype
              This  is a copy of the af parameter to getipnodeby-
              name(e)  or  getipnodebyaddr(r).   h_addrtype  will
              always  be AF_INET if the af parameter was AF_INET.
              h_addrtype will always be AF_INET6 if the af param-
              eter was AF_INET6.

       h_length
              This field will be set to sizeof(struct in_addr) if
              h_addrtype  is  AF_INET,   and   to   sizeof(struct
              in6_addr) if h_addrtype is AF_INET6.

       h_addr_list
              This is an array of one or more pointers to network
              address structures for the network host.  The array
              is terminated by a null pointer.

SEE ALSO
       getaddrinfo(o), inet_ntop(p), inet_pton(n)



Linux Man Page              2000-12-18         getipnodebyname(e)