ypclnt(3n) DG/UX 4.30 ypclnt(3n)
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 - Yellow Pages client interface
SYNOPSIS AND DESCRIPTION
This package of functions provides an interface to the
Yellow Pages (YP) network lookup service. The package can
be loaded from the standard library, /usr/lib/libc.a. Refer
to ypfiles(5) and ypserv(8) 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
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 0 if they
succeed, and a failure code (YPERRxxxx) otherwise. Failure
codes are described under DIAGNOSTICS below.
ypbind (indomain);
char *indomain;
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 (for example, a local file) in cases when YP
services are not available.
void
ypunbind (indomain)
char *indomain;
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
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available at the client interface 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.
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 cannot 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.
ypgetdefaultdomain (outdomain);
char **outdomain;
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.
ypmatch(indomain, inmap, inkey, inkeylen, outval, outvallen)
char *indomain;
char *inmap;
char *inkey;
int inkeylen;
char **outval;
int *outvallen;
ypmatch() returns the value associated with a passed
key. This key must be exact; no pattern matching is
available.
ypfirst(indomain, inmap, outkey, outkeylen, outval, outvallen)
char *indomain;
char *inmap;
char **outkey;
int *outkeylen;
char **outval;
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int *outvallen;
ypfirst() returns the first key-value pair from the
named map in the named domain.
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;
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
particular to the structure of the YP map being
processing; there is no relation in retrieval order to
either the lexical 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 reason
of YPERRNOMORE, 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 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.
ypall(indomain, inmap, incallback);
char *indomain;
char *inmap;
struct ypallcallback incallback;
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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 transaction 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 function 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
unsuccessfully), or your foreach function decides that
it does not 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
(base YP_TRUE) 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 will not
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
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YP 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 ypall() is then 0.
yporder(indomain, inmap, outorder);
char *indomain;
char *inmap;
int *outorder;
yporder() returns the order number for a map.
ypmaster(indomain, inmap, outname);
char *indomain;
char *inmap;
char **outname;
ypmaster() returns the machine name of the master YP
server for a map.
char *yperrstring(incode)
int incode;
yperrstring() returns a pointer to an error message
string that is NULL-terminated but contains no period
or NEWLINE.
ypproterr (incode)
unsigned int incode;
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
/usr/lib/libc.a
SEE ALSO
malloc(3c), ypupdate(3N), ypfiles(5), ypserv(8)
DIAGNOSTICS
All integer functions return 0 if the requested operation is
successful, or one of the following errors if the operation
fails.
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ypclnt(3n) DG/UX 4.30 ypclnt(3n)
#define YPERRBADARGS
1 /* args to function are bad
#define YPERRRPC
2 /* RPC failure - domain has
#define YPERRDOMAIN
3 /* can't bind to server on
#define YPERRMAP
4 /* no such map in server's
#define YPERRKEY
5 /* no such key in map
#define YPERRYPERR
6 /* internal yp server or client
#define YPERRRESRC
7 /* resource allocation failure */
#define YPERRNOMORE
8 /* no more records in map
#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
#define YPERRBADDBfR
13 /* yp database is bad */
#define YPERRVERSfR
14 /* yp version mismatch */
#define YPERRACCESS
15 /* access violation */
#define YPERRBUSY
16 /* database busy */
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