
GETHOSTBYNAME(3)           UNIX Programmer's Manual           GETHOSTBYNAME(3)

NNAAMMEE
     ggeetthhoossttbbyynnaammee, ggeetthhoossttbbyyaaddddrr, ggeetthhoosstteenntt, sseetthhoosstteenntt, eennddhhoosstteenntt, hheerrrroorr
     - get network host entry

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<nneettddbb..hh>>
     eexxtteerrnn ssttrruucctt hh__eerrrrnnoo;;

     _s_t_r_u_c_t _h_o_s_t_e_n_t _*
     ggeetthhoossttbbyynnaammee(_c_h_a_r _*_n_a_m_e)

     _s_t_r_u_c_t _h_o_s_t_e_n_t _*
     ggeetthhoossttbbyyaaddddrr(_c_h_a_r _*_a_d_d_r, _i_n_t _l_e_n, _i_n_t _t_y_p_e)

     _s_t_r_u_c_t _h_o_s_t_e_n_t _*
     ggeetthhoosstteenntt(_v_o_i_d)

     sseetthhoosstteenntt(_i_n_t _s_t_a_y_o_p_e_n)

     eennddhhoosstteenntt(_v_o_i_d)

     hheerrrroorr(_c_h_a_r _*_s_t_r_i_n_g)

DDEESSCCRRIIPPTTIIOONN
     The ggeetthhoossttbbyynnaammee() and ggeetthhoossttbbyyaaddddrr() functions each return a pointer
     to an object with the following structure describing an internet host
     referenced by name or by address, respectively.  This structure contains
     either the information obtained from the name server, named(8),  or bro-
     ken-out fields from a line in _/_e_t_c_/_h_o_s_t_s. If the local name server is not
     running these routines do a lookup in _/_e_t_c_/_h_o_s_t_s.

     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 from name server */
     };
     #define h_addr  h_addr_list[0]  /* address, for backward compatibility */

     The members of this structure are:

     _h___n_a_m_e       Official name of the host.

     _h___a_l_i_a_s_e_s    A zero terminated array of alternate names for the host.

     _h___a_d_d_r_t_y_p_e   The type of address being returned; currently always
                  AF_INET.

     _h___l_e_n_g_t_h     The length, in bytes, of the address.

     _h___a_d_d_r___l_i_s_t  A zero terminated array of network addresses for the host.
                  Host addresses are returned in network byte order.

     _h___a_d_d_r       The first address in _h___a_d_d_r___l_i_s_t; this is for backward com-
                  patiblity.

                  When using the nameserver, ggeetthhoossttbbyynnaammee() will search for
                  the named host in the current domain and its parents unless
                  the name ends in a dot.  If the name contains no dot, and if
                  the environment variable ``HOSTALIASES'' contains the name
                  of an alias file, the alias file will first be searched for
                  an alias matching the input name.  See hostname(7) for the
                  domain search procedure and the alias file format.

                  The sseetthhoosstteenntt() function may be used to request the use of
                  a connected TCP socket for queries.  If the _s_t_a_y_o_p_e_n flag is
                  non-zero, this sets the option to send all queries to the
                  name server using TCP and to retain the connection after
                  each call to ggeetthhoossttbbyynnaammee() or ggeetthhoossttbbyyaaddddrr().  Otherwise,
                  queries are performed using UDP datagrams.

                  The eennddhhoosstteenntt() function closes the TCP connection.

FFIILLEESS
     /etc/hosts

DDIIAAGGNNOOSSTTIICCSS
     Error return status from ggeetthhoossttbbyynnaammee() and ggeetthhoossttbbyyaaddddrr() is indicated
     by return of a null pointer.  The external integer _h___e_r_r_n_o may then be
     checked to see whether this is a temporary failure or an invalid or un-
     known host.  The routine hheerrrroorr() can be used to print an error message
     describing the failure.  If its argument _s_t_r_i_n_g is non-NULL, it is print-
     ed, followed by a colon and a space.  The error message is printed with a
     trailing newline.

     The variable _h___e_r_r_n_o can have the following values:

     HOST_NOT_FOUND  No such host is known.

     TRY_AGAIN       This is usually a temporary error and means that the lo-
                     cal server did not receive a response from an authorita-
                     tive server.  A retry at some later time may succeed.

     NO_RECOVERY     Some unexpected server failure was encountered.  This is
                     a non-recoverable error.

     NO_DATA         The requested name is valid but does not have an IP ad-
                     dress; this is not a temporary error.  This means that
                     the name is known to the name server but there is no ad-
                     dress associated with this name.  Another type of request
                     to the name server using this domain name will result in
                     an answer; for example, a mail-forwarder may be regis-
                     tered for this domain.

SSEEEE AALLSSOO
     resolver(3),  hosts(5),  hostname(7),  named(8)

CCAAVVEEAATT
     The ggeetthhoosstteenntt() function is defined, and sseetthhoosstteenntt() and eennddhhoosstteenntt()
     are redefined, when libc(3) is built to use only the routines to lookup
     in _/_e_t_c_/_h_o_s_t_s and not the name server.

     The ggeetthhoosstteenntt() function reads the next line of _/_e_t_c_/_h_o_s_t_s, opening the
     file if necessary.

     The sseetthhoosstteenntt() function is redefined to open and rewind the file.  If
     the _s_t_a_y_o_p_e_n argument is non-zero, the hosts data base will not be closed
     after each call to ggeetthhoossttbbyynnaammee() or ggeetthhoossttbbyyaaddddrr().  The eennddhhoosstteenntt()
     function is redefined to close the file.

HHIISSTTOORRYY
     The hheerrrroorr() function appeared in 4.3BSD. The eennddhhoosstteenntt(),
     ggeetthhoossttbbyyaaddddrr(), ggeetthhoossttbbyynnaammee(), ggeetthhoosstteenntt(), and sseetthhoosstteenntt() func-
     tions appeared in 4.2BSD.

BBUUGGSS
     These functions use static data storage; if the data is needed for future
     use, it should be copied before any subsequent calls overwrite it.  Only
     the Internet address format is currently understood.

 MiNT-Net                        July 31, 1991                               3































































