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BSD 2.11 - man page for sethostent (bsd section 3)

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GETHOSTBYNAME(3)								 GETHOSTBYNAME(3)

NAME
       gethostbyname,  gethostbyaddr,  gethostent,  sethostent,  endhostent, herror - get network
       host entry

SYNOPSIS
       #include <netdb.h>

       extern int h_errno;

       struct hostent *gethostbyname(name)
       char *name;

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

       struct hostent *gethostent()

       sethostent(stayopen)
       int stayopen;

       endhostent()

       herror(string)
       char *string;

DESCRIPTION
       Gethostbyname and gethostbyaddr 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
       broken-out  fields  from  a  line  in /etc/hosts.  If the local name server is not running
       these routines do a lookup in /etc/hosts.

	      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_name	    Official name of the host.

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

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

       h_length     The length, in bytes, of the address.

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

       h_addr	    The first address in h_addr_list; this is for backward compatiblity.

       When  using  the  nameserver,  gethostbyname 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.

       Sethostent  may	be used to request the use of a connected TCP socket for queries.  If the
       stayopen 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 gethostbyname or gethostbyaddr.
       Otherwise, queries are performed using UDP datagrams.

       Endhostent closes the TCP connection.

DIAGNOSTICS
       Error return status from gethostbyname and gethostbyaddr is indicated by return of a  null
       pointer.  The external integer h_errno may then be checked to see whether this is a tempo-
       rary failure or an invalid or unknown host.  The routine herror can be used  to	print  an
       error  message describing the failure.  If its argument string is non-NULL, it is printed,
       followed by a colon and a space.  The error message is printed with a trailing newline.

       h_errno 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  local  server
			      did  not	receive a response from an authoritative 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 address; this
			      is not a temporary error.  This means that the name is known to the
			      name  server  but  there	is  no address 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 reg-
			      istered for this domain.

FILES
       /etc/hosts

SEE ALSO
       resolver(3), hosts(5), hostname(7), named(8)

CAVEAT
       Gethostent is defined, and sethostent and endhostent are redefined, when libc is built  to
       use only the routines to lookup in /etc/hosts and not the name server.

       Gethostent reads the next line of /etc/hosts, opening the file if necessary.

       Sethostent  is  redefined  to  open and rewind the file.  If the stayopen argument is non-
       zero, the hosts data base will not be closed after each call to gethostbyname or  gethost-
       byaddr.	Endhostent is redefined to close the file.

BUGS
       All  information  is contained in a static area so it must be copied if it is to be saved.
       Only the Internet address format is currently understood.

4.2 Berkeley Distribution		 October 30, 1996			 GETHOSTBYNAME(3)
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