ypclnt(3N) NETWORK FUNCTIONS ypclnt(3N)
NAME
ypclnt, ypgetdefaultdomain, ypbind, ypunbind, ypmatch,
ypfirst, ypnext, ypall, yporder, ypmaster,
yperrstring, ypproterr - YP client interface
SYNOPSIS
#include <rpcsvc/ypclnt.h>
#include <rpcsvc/ypprot.h>
DESCRIPTION
This package of functions provides an interface to the YP
network lookup service. The package can be loaded from the
standard library, /usr/lib/libnsl.{so,a}. Refer to
ypfiles(4) and ypserv(1M) for an overview of the YP name
services, including the definitions of map and domain, and a
description of the various servers, databases, and commands
that comprise the YP name service. 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(3), and may be freed if
the user code has no continuing need for it. For each out-
key 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.
Routines
ypbind (indomain);
char *indomain;
To use the YP name 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
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descriptor. However, multiple requests to the same
domain use that same descriptor. ypunbind() is avail-
able at the client interface for processes that expli-
citly 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
⊕ the client process cannot bind a server for the
proper domain, or
⊕ 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 pro-
cess 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
name service 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 pro-
cessing; there is no relation in retrieval order to
either the lexical order within any original (non-YP
name service) 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. ypall() can be used just like any other
YP name service procedure, identify the map in the nor-
mal manner, and supply the name of a function which
will be called to process each key-value pair within
the map. The call to ypall() returns only when the
transaction is completed (successfully or unsuccess-
fully), or the 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 invallen;
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 name service 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
YP client package inspects its contents - cast it to
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something useful, or ignore it.
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 name service 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/lib/libyp.a
SEE ALSO
ypserv(1M), malloc(3), ypupdate(3N), ypfiles(4)
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
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"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 rpcbinder */"
#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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