freehostent

GETIPNODEBYNAME(3)         Linux Programmer's Manual        GETIPNODEBYNAME(3)

NAME
       getipnodebyname,  getipnodebyaddr,  freehostent - get network hostnames
       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
       These functions are deprecated (and unavailable in glibc).  Use  getad-
       drinfo(3) and getnameinfo(3) instead.

       The  getipnodebyname() and getipnodebyaddr() 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(3) and gethostbyaddr(3) func-
       tions, which could access only the IPv4 network  address  family.   The
       getipnodebyname()  and  getipnodebyaddr() functions can access multiple
       network address families.

       Unlike the gethostby functions, these functions return pointers to  dy-
       namically  allocated memory.  The freehostent() function is used to re-
       lease the dynamically allocated memory after the caller no longer needs
       the hostent structure.

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

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

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

       The  flags argument specifies additional options.  More than one option
       can be specified by bitwise 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 ad-
              dresses 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_DEFAULT
              This flag is equivalent to (AI_ADDRCONFIG | AI_V4MAPPED).

   getipnodebyaddr() arguments
       The getipnodebyaddr() function looks up the name of the host whose net-
       work address is specified by the addr argument.  The af argument speci-
       fies one of the following values:

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

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

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

       HOST_NOT_FOUND
              The hostname 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 in-
              formation 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 structure that con-
       tains 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  argument to getipnodebyname() or
              getipnodebyaddr().  h_addrtype will always be AF_INET if the  af
              argument was AF_INET.  h_addrtype will always be AF_INET6 if the
              af argument 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.

CONFORMING TO
       RFC 2553.

NOTES
       These functions were present  in  glibc  2.1.91-95,  but  were  removed
       again.   Several UNIX-like systems support them, but all call them dep-
       recated.

SEE ALSO
       getaddrinfo(3), getnameinfo(3), inet_ntop(3), inet_pton(3)

COLOPHON
       This page is part of release 5.05 of the Linux  man-pages  project.   A
       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.

Linux                             2017-09-15                GETIPNODEBYNAME(3)