YPCLNT(NS) System V NFS (11/30/90) YPCLNT(NS)
NAME
ypclnt yp_get_default_domain yp_bind yp_unbind yp_match
yp_first yp_next yp_all yp_order yp_master yperr_string
ypprot_err - network information service client interface
SYNOPSIS
#include <rpcsvc/ypclnt.h>
ypbind(indomain)
char *indomain;
void ypunbind(indomain)
char *indomain;
ypgetdefaultdomain(outdomain)
char **outdomain;
ypmatch(indomain, inmap, inkey, inkeylen, outval, outvallen)
char *indomain;
char *inmap;
char *inkey;
int inkeylen;
char **outval;
int *outvallen;
ypfirst(indomain, inmap, outkey, outkeylen, outval, outvallen)
char *indomain;
char *inmap;
char **outkey;
int *outkeylen;
char **outval;
int *outvallen;
ypnext(indomain, inmap, inkey, inkeylen, outkey, outkeylen, outval, outvallen)
char *indomain;
char *inmap;
char *inkey;
int inkeylen;
char **outkey;
int *outkeylen;
char **outval;
int *outvallen;
ypall(indomain, inmap, incallback)
char *indomain;
char *inmap;
struct ypallcallback incallback;
yporder(indomain, inmap, outorder)
char *indomain;
char *inmap;
int *outorder;
ypmaster(indomain, inmap, outname)
char *indomain;
char *inmap;
char **outname;
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char *yperrstring(incode)
int incode;
ypproterr(incode)
unsigned int incode;
DESCRIPTION
This package of functions provides an interface to the
network information service (NIS) network lookup service.
The package can be loaded from the standard library,
/usr/lib/libyp.a. The RPC library, /usr/lib/librpc.a, and
the transport library will probably need to be linked in as
well. Refer to ypfiles(NF) and ypserv(NADM) for an overview
of the network information service, including the
definitions of map and domain, as well as a description of
the various servers, databases, and commands that comprise
the NIS.
All input parameters names begin with in. Output parameters
begin with out. Output parameters of type char ** should be
addresses of uninitialized character pointers. Memory is
allocated by the NIS client package using malloc(S), and may
be freed if the user code has no continuing need for it. For
each outkey and outval, two extra bytes of memory are
allocated at the end that contain NEWLINE and NULL,
respectively, but these two bytes are not reflected in
outkeylen or outvallen. indomain and inmap strings must be
non-null and null-terminated. String parameters which are
accompanied by a count parameter may not be null, but may
point to null strings, with the count parameter indicating
this. Counted strings need not be null-terminated.
All functions in this package of type int return zero if
they succeed and a failure code (YPERR_xxxx) otherwise.
These failure codes are described under DIAGNOSTICS below.
The NIS lookup calls require at least a map name and a
domain name. It is assumed that the client process knows the
name of the map of interest. Client processes should fetch
the node's default domain by calling ypgetdefaultdomain()
and use the returned outdomain as the indomain parameter to
successive NIS calls.
To use the NIS services, the client process must be
``bound'' to a NIS server that serves the appropriate domain
using yp_bind. Binding need not be done explicitly by user
code; this is done automatically whenever a NIS lookup
function is called. yp_bind can be called directly for
processes that make use of a backup strategy (e.g., a local
file) in cases when NIS services are not available.
Each binding allocates (uses up) one client process socket
descriptor; each bound domain costs one socket descriptor.
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However, multiple requests to the same domain use the same
descriptor. yp_unbind() is available at the client
interface for processes that explicitly manage their socket
descriptors while accessing multiple domains. The call to
yp_unbind() make the domain unbound and free all per-process
and per-node resources used to bind it.
If an RPC failure results upon use of a binding, that domain
will be unbound automatically. At that point, the ypclnt
layer will retry forever or until the operation succeeds,
provided that ypbind is running and either
a) the client process can't bind a server for the proper
domain, or
b) RPC requests to the server fail.
If an error is not RPC-related, or if ypbind is not running,
or if a bound ypserv process returns any answer (success or
failure), the ypclnt layer will return control to the user
code, either with an error code, or a success code and any
results.
yp_match returns the value associated with a passed key.
This key must be exact; no pattern matching is available.
yp_first returns the first key-value pair from the named map
in the named domain.
yp_next() returns the next key-value pair in a named map.
The inkey parameter should be the outkey returned from an
initial call to yp_first() (to get the second key-value
pair) or the one returned from the nth call to yp_next() (to
get the nth + second key-value pair).
The concept of first (and, for that matter, of next) is
particular to the structure of the NIS map being processing;
there is no relation in retrieval order to either the
lexical order within any original (non-NIS) data base, or to
any obvious numerical sorting order on the keys, values, or
key-value pairs. The only ordering guarantee made is that
if the yp_first() function is called on a particular map and
then the yp_next() function is called repeatedly on the same
map at the same server until the call fails with a reason of
YPERR_NOMORE, every entry in the data base will be seen
exactly once. Further, if the same sequence of operations is
performed on the same map at the same server, the entries
will be seen in the same order.
Under conditions of heavy server load or server failure, it
is possible for the domain to become unbound, then bound
once again (perhaps to a different server) while a client is
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running. This can cause a break in one of the enumeration
rules; specific entries may be seen twice by the client, or
not at all. This approach protects the client from error
messages that would otherwise be returned in the midst of
the enumeration. The next paragraph describes a better
solution to enumerating all entries in a map.
yp_all provides a way to transfer an entire map from server
to client in a single request using TCP (rather than UDP as
with other functions in this package). The entire
transaction take place as a single RPC request and response.
You can use yp_all just like any other NIS procedure,
identify the map in the normal manner, and supply the name
of a function which will be called to process each key-value
pair within the map. You return from the call to yp_all
only when the transaction is completed (successfully or
unsuccessfully), or your ``foreach'' function decides that
it does not want to see any more key-value pairs.
The third parameter to yp_all is
struct ypallcallback *incallback {
int (*foreach)();
char *data;
};
The function foreach is called
foreach(instatus, inkey, inkeylen, inval, invallen, indata)
int instatus;
char *inkey;
int inkeylen;
char *inval;
int invallen;
char *indata;
The instatus parameter will hold one of the return status
values defined in <rpcsvc/yp_prot.h> - either YP_TRUE or an
error code. (See ypprot_err, below, for a function which
converts a NIS protocol error code to a ypclnt layer error
code.)
The key and value parameters are somewhat different than
defined in the synopsis section above. First, the memory
pointed to by the inkey and inval parameters is private to
the yp_all function and is overwritten with the arrival of
each new key-value pair. It is the responsibility of the
foreach function to do something useful with the contents of
that memory, but it does not own the memory itself. The key
and value objects presented to the foreach function look
exactly as they do in the server's map - if they were not
newline-terminated or null-terminated in the map, they won't
be here either.
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The indata parameter is the contents of the incallback->data
element passed to yp_all . The data element of the callback
structure may be used to share state information between the
foreach function and the mainline code. Its use is optional
and no part of the NIS client package inspects its contents
- cast it to something useful or ignore it as you see fit.
The foreach function is a Boolean. It should return zero to
indicate that it wants to be called again for further
received key-value pairs or non-zero to stop the flow of
key-value pairs. If foreach returns a non-zero value, it is
not called again; the functional value of yp_all is then 0.
yp_order returns the order number for a map.
yp_master returns the machine name of the master NIS server
for a map.
yperr_string returns a pointer to an error message string
that is null-terminated but contains no period or newline.
ypprot_err takes a NIS protocol error code as input and
returns a ypclnt layer error code, which may be used in turn
as an input to yperr_string.
FILES
/usr/include/rpcsvc/ypclnt.h
/usr/include/rpcsvc/yp_prot.h
SEE ALSO
ypfiles(NF), ypserv(NADM)
DIAGNOSTICS
All integer functions return 0 if the requested operation is
successful, or one of the following errors if the operation
fails.
#define YPERR_BADARGS 1 /* args to function are bad */
#define YPERR_RPC 2 /* RPC failure - domain has been unbound */
#define YPERR_DOMAIN 3 /* cannot bind to server on this domain */
#define YPERR_MAP 4 /* no such map in server's domain */
#define YPERR_KEY 5 /* no such key in map */
#define YPERR_YPERR 6 /* internal NIS server or client error */
#define YPERR_RESRC 7 /* resource allocation failure */
#define YPERR_NOMORE 8 /* no more records in map database */
#define YPERR_PMAP 9 /* cannot communicate with portmapper */
#define YPERR_YPBIND 10 /* cannot communicate with ypbind */
#define YPERR_YPSERV 11 /* cannot communicate with ypserv */
#define YPERR_NODOM 12 /* local domain name not set */
#define YPERR_BADDB 13 /* NIS data base is bad */
#define YPERR_VERS 14 /* NIS version mismatch */
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