ypclnt(3N) NFS ypclnt(3N)
NAME
ypclnt, ypgetdefaultdomain, ypbind, ypunbind, ypmatch,
ypfirst, ypnext, ypall, yporder, ypmaster,
yperrstring, ypproterr - yellow pages 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;
char *yperrstring(incode)
int incode;
ypproterr(incode)
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unsigned int incode;
DESCRIPTION
This package of functions provides an interface to the yel-
low pages (YP) network lookup service. The package can be
loaded from the standard library, /lib/libc.a. Refer to
ypfiles(4) and ypserv(1M) for an overview of the yellow
pages, including the definitions of map and domain, and a
description of the various servers, databases, and commands
that comprise the YP.
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 YP client package using malloc(3C), 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 allo-
cated at the end that contain NEWLINE and NULL, respec-
tively, 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 accom-
panied 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 0 if they
succeed, and a failure code (YPERR_xxxx) otherwise. Failure
codes are described under DIAGNOSTICS below.
The YP lookup calls require a map name and a domain name, at
minimum. 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 YP calls.
To use the YP services, the client process must be ``bound''
to a YP server that serves the appropriate domain using
ypbind. Binding need not be done explicitly by user code;
this is done automatically whenever a YP lookup function is
called. ypbind can be called directly for processes that
make use of a backup strategy (e.g., a local file) in cases
when YP services are not available.
Each binding allocates (uses up) one client process socket
descriptor; each bound domain costs one socket descriptor.
However, multiple requests to the same domain use that same
descriptor. ypunbind() is available at the client inter-
face for processes that explicitly manage their socket
descriptors while accessing multiple domains. The call to
ypunbind() make the domain unbound, and free all per-
process and per-node resources used to bind it.
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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.
ypmatch returns the value associated with a passed key.
This key must be exact; no pattern matching is available.
ypfirst returns the first key-value pair from the named map
in the named domain.
ypnext() returns the next key-value pair in a named map.
The inkey parameter should be the outkey returned from an
initial call to ypfirst() (to get the second key-value
pair) or the one returned from the nth call to ypnext() (to
get the nth + second key-value pair).
The concept of first (and, for that matter, of next) is par-
ticular to the structure of the YP map being processing;
there is no relation in retrieval order to either the lexi-
cal order within any original (non-YP) 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 ypfirst() function is called on a particular map,
and then the ypnext() function is repeatedly called on the
same map at the same server until the call fails with a rea-
son of YPERR_NOMORE, every entry in the data base will be
seen exactly once. Further, if the same sequence of opera-
tions 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
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.
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ypall 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 transac-
tion take place as a single RPC request and response. You
can use ypall just like any other YP procedure, identify
the map in the normal manner, and supply the name of a func-
tion which will be called to process each key-value pair
within the map. You return from the call to ypall only
when the transaction is completed (successfully or unsuc-
cessfully), or your foreach function decides that it doesn't
want to see any more key-value pairs.
The third parameter to ypall 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 invalllen;
char *indata;
The instatus parameter will hold one of the return status
values defined in <rpcsvc/ypprot.h> - either YPTRUE or an
error code. (See ypproterr, below, for a function which
converts a YP 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 ypall 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. 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.
The indata parameter is the contents of the incallback->data
element passed to ypall. 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 YP client package inspects its
contents - cast it to something useful, or ignore it as you
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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 ypall is then 0.
yporder returns the order number for a map.
ypmaster returns the machine name of the master YP server
for a map.
yperrstring returns a pointer to an error message string
that is null-terminated but contains no period or newline.
ypproterr takes a YP protocol error code as input, and
returns a ypclnt layer error code, which may be used in turn
as an input to yperrstring.
FILES
/usr/include/rpcsvc/ypclnt.h
/usr/include/rpcsvc/ypprot.h
SEE ALSO
ypfiles(4), ypserv(1M),
DIAGNOSTICS
All integer functions return 0 if the requested operation is
successful, or one of the following errors if the operation
fails.
#define YPERRBADARGS 1 /* args to function are bad */
#define YPERRRPC 2 /* RPC failure - domain has been
unbound */
#define YPERRDOMAIN 3 /* can't bind to server on this domain */
#define YPERRMAP 4 /* no such map in server's domain */
#define YPERRKEY 5 /* no such key in map */
#define YPERRYPERR 6 /* internal yp server or client error */
#define YPERRRESRC 7 /* resource allocation failure */
#define YPERRNOMORE 8 /* no more records in map database */
#define YPERRPMAP 9 /* can't communicate with portmapper */
#define YPERRYPBIND 10 /* can't communicate with ypbind */
#define YPERRYPSERV 11 /* can't communicate with ypserv */
#define YPERRNODOM 12 /* local domain name not set */
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