gethostbyname man page on 4.4BSD

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       gethostbyname,  gethostbyaddr, gethostent, sethostent, endhostent, her‐
       ror - get network host entry

       #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()

       int stayopen;


       char *string;

       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 infor‐
       mation  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

       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

       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 ``HOSTALA‐
       IASES''	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 connec‐
       tion after each call to	gethostbyname  or  gethostbyaddr.   Otherwise,
       queries are performed using UDP datagrams.

       Endhostent closes the TCP connection.

       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 temporary 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
			      registered for this domain.


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

       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  nec‐

       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  gethostbyaddr.  Endhostent is redefined to
       close the file.

       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

4.2 Berkeley Distribution	 June 23, 1990		      GETHOSTBYNAME(3)

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