ENDHOSTENT(3XNET) X/Open Networking Services Library Functions


NAME


endhostent, gethostbyaddr, gethostbyname, gethostent, sethostent -
network host database functions

SYNOPSIS


cc [ flag ... ] file ... -lxnet [ library ... ]
#include <netdb.h>
extern int h_errno;

void endhostent(void)


struct hostent *gethostbyaddr(const void *addr, socklen_t len, int type);


struct hostent *gethostbyname(const char *name);


struct hostent *gethostent(void)


void sethostent(int stayopen);


DESCRIPTION


The gethostent(), gethostbyaddr(), and gethostbyname() functions each
return a pointer to a hostent structure, the members of which contain the
fields of an entry in the network host database.


The gethostent() function reads the next entry of the database, opening a
connection to the database if necessary.


The gethostbyaddr() function searches the database and finds an entry
which matches the address family specified by the type argument and which
matches the address pointed to by the addr argument, opening a
connection to the database if necessary. The addr argument is a pointer
to the binary-format (that is, not null-terminated) address in network
byte order, whose length is specified by the len argument. The datatype
of the address depends on the address family. For an address of type
AF_INET, this is an in_addr structure, defined in <netinet/in.h>. For an
address of type AF_INET6, there is an in6_addr structure defined in
<netinet/in.h>.


The gethostbyname() function searches the database and finds an entry
which matches the host name specified by the name argument, opening a
connection to the database if necessary. If name is an alias for a valid
host name, the function returns information about the host name to which
the alias refers, and name is included in the list of aliases returned.


The sethostent() function opens a connection to the network host
database, and sets the position of the next entry to the first entry. If
the stayopen argument is non-zero, the connection to the host database
will not be closed after each call to gethostent() (either directly, or
indirectly through one of the other gethost*() functions).


The endhostent() function closes the connection to the database.

USAGE


The gethostent(), gethostbyaddr(), and gethostbyname() functions may
return pointers to static data, which may be overwritten by subsequent
calls to any of these functions.


These functions are generally used with the Internet address family.

RETURN VALUES


On successful completion, gethostbyaddr(), gethostbyname() and
gethostent() return a pointer to a hostent structure if the requested
entry was found, and a null pointer if the end of the database was
reached or the requested entry was not found. Otherwise, a null pointer
is returned.


On unsuccessful completion, gethostbyaddr() and gethostbyname() functions
set h_errno to indicate the error.

ERRORS


No errors are defined for endhostent(), gethostent() and sethostent().


The gethostbyaddr() and gethostbyname() functions will fail in the
following cases, setting h_errno to the value shown in the list below.
Any changes to errno are unspecified.

HOST_NOT_FOUND
No such host is known.


NO_DATA
The server recognised the request and the name but no
address is available. Another type of request to the
name server for the domain might return an answer.


NO_RECOVERY
An unexpected server failure occurred which can not be
recovered.


TRY_AGAIN
A temporary and possibly transient error occurred, such
as a failure of a server to respond.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+

SEE ALSO


endservent(3XNET), htonl(3XNET), inet_addr(3XNET), attributes(5),
standards(5)


November 1, 2003 ENDHOSTENT(3XNET)