GETHOSTBYADDR(3n,L)         AIX Technical Reference         GETHOSTBYADDR(3n,L)



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gethostbyaddr, gethostbyname, sethostent, endhostent



PURPOSE

Get network host entry.

LIBRARY

Internet Library (libc.a)

SYNTAX

#include <netdb.h>


   struct hostent *gethostbyaddr(addr, len, type)     void sethostent(stayopen)
   char *addr;                                        int stayopen;
   int len, type;
                                                      void endhostent()
   struct hostent *gethostbyname(name)
   char *name;



DESCRIPTION

The gethostbyname and gethostbyaddr subroutines each return a pointer to an
object.  This object is a hostent structure, which contains information
obtained from the name server program, or a field from a line in the /etc/hosts
file (the network host data base).  If the local name server is not running,
these routines do a lookup in /etc/hosts.

The hostent structure is defined in the netdb.h header file, and it contains
the following members:

          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 from name server */

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

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.




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GETHOSTBYADDR(3n,L)         AIX Technical Reference         GETHOSTBYADDR(3n,L)



h_addrtype
          The type of address being returned.  The subroutine always sets this
          value to AF_INET.

h_length  The length, in bytes, of the address.

h_addr_list
          An array, terminated by 0, of pointers to the network addresses for
          the host.  Host addresses are returned in network byte order.

h_addr    The first address in h_addr_list, provided for backward
          compatibility.

The sethostent subroutine allows a request for the use of a connected socket
using TCP for queries.  If the stayopen parameter is nonzero, an option is set
to send all queries to the name server using TCP and to retain the connection
after each call to gethostbyname or gethostbyaddr.

The endhostent subroutine closes the TCP connection.

The gethostbyname and gethostbyaddr subroutines query the name server or search
the file sequentially from its beginning until finding a matching host name or
host address, or until encountering the end of the file.  Host addresses are
supplied in network order.

RETURN VALUE

The gethostbyname and gethostbyaddr subroutines return a pointer to a hostent
structure on success.

Note:  The return value points to static data that is overwritten by subsequent
       calls.

A NULL pointer (0) is returned if an error occurs or the end of the file is
reached and the h_errno variable is set to indicate the error.

ERROR CONDITIONS

The gethostbyname and gethostbyaddr subroutines fail if one or more of the
following are true:

HOST_NOT_FOUND
        The host specified by the name parameter was not found.

TRY_AGAIN
        The local server did not receive a response from an authoritative
        server.  Try again later.

NO_RECOVERY
        This error code indicates an unrecoverable error.





Processed July 12, 1991       GETHOSTBYADDR(3n,L)                             2






GETHOSTBYADDR(3n,L)         AIX Technical Reference         GETHOSTBYADDR(3n,L)



NO_ADDRESS
        The requested name is valid but does not have an Internet address at
        the name server.

FILES

/etc/hosts  Host name data base.

/etc/resolv.conf
            Name server and domain name data base.

RELATED INFORMATION

In this book:  "Related Network Publications."

The discussion of host, named, and resolv.conf in AIX TCP/IP User's Guide.







































Processed July 12, 1991       GETHOSTBYADDR(3n,L)                             3