ypclnt(3yp) ypclnt(3yp)
Name
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 package
Syntax
#include <rpcsvc/ypclnt.h>
yp_get_default_domain(outdomain)
char **outdomain;
yp_bind(indomain)
char *indomain;
void yp_unbind(indomain)
char *indomain;
yp_match(indomain, inmap, inkey, inkeylen, outval, outvallen)
char *indomain;
char *inmap;
char *inkey;
int inkeylen;
char **outval;
int *outvallen;
yp_first(indomain, inmap, outkey, outkeylen, outval, outvallen)
char *indomain;
char *inmap;
char **outkey;
int *outkeylen;
char **outval;
int *outvallen;
yp_next(indomain, inmap, inkey, inkeylen, outkey, outkeylen, outval, outvallen)
char *indomain;
char *inmap;
char *inkey;
int inkeylen;
char **outkey;
int *outkeylen;
char **outval;
int *outvallen;
yp_all(indomain, inmap, incallback)
char *indomain;
char *inmap;
struct ypall_callback incallback;
yp_order(indomain, inmap, outorder)
char *indomain;
char *inmap;
int *outorder;
yp_master(indomain, inmap, outname)
char *indomain;
char *inmap;
char **outname;
char *yperr_string(incode)
int incode;
ypprot_err(incode)
unsigned int incode;
Description
This package of functions provides an interface to the Yellow Pages (YP) data base lookup service. The package can be loaded from the
standard library, Refer to and for an overview of the Yellow Pages, including the definitions of map and domain, and for a description of
the servers, data bases, and commands that constitute the YP application.
All input parameters names begin with in. Output parameters begin with out. Output parameters of type char ** should be addresses of
uninitialized character pointers. The YP client package allocates memory using This memory can 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. The indomain and inmap strings must be non-null and null-terminated.
String parameters that are accompanied by a count parameter cannot be null, but can point to null strings, with the count parameter indi-
cating this. Counted strings need not be null-terminated.
All functions of type int return 0 if they succeed, or a failure code (YPERR_ xxxx ) if they do not succeed. Failure codes are described
under Diagnostics.
The YP lookup calls require a map name and a domain name. It is assumed that the client process knows the name of the map of interest.
Client processes fetch the node's default domain by calling and use the returned outdomain as the indomain parameter to successive YP
calls.
To use YP services, the client process must be bound to a YP server that serves the appropriate domain. The binding is accomplished with
Binding need not be done explicitly by user code; it is done automatically whenever a YP lookup function is called. The function can be
called directly for processes that make use of a backup strategy in cases when YP services are not available.
Each binding allocates one client process socket descriptor; each bound domain requires one socket descriptor. Multiple requests to the
same domain use that same descriptor. The function is available at the client interface for processes that explicitly manage their socket
descriptors while accessing multiple domains. The call to makes the domain unbound, and frees 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. This action occurs provided that is running, and either the client process cannot bind a server
for the proper domain, or RPC requests to the server fail.
The -s option allows the system administrator to lock to a particular domain and set of servers. Up to four servers can be specified. An
example of the -s option follows:
/etc/ypbind -s domain,server1[,server2,server3,server4]
The ypclnt layer will return control to the user code, either with an error code, or with a success code and any results under certain cir-
cumstances. For example, control will be returned to the user code when an error is not RPC-related and also when the function is not run-
ning. An additional situation that will cause the return of control is when a bound ypserv process returns any answer (success or fail-
ure).
The function returns the value associated with a passed key. This key must be exact; no pattern matching is available.
The function returns the first key-value pair from the named map in the named domain.
The function returns the next key-value pair in a named map. The inkey parameter should be the outkey returned from an initial call to (to
get the second key-value pair) or the one returned from the nth call to (to get the nth + second key-value pair).
The concept of first and of next is particular to the structure of the YP map being processed; 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 function is called on a particular map, and then the function is repeatedly
called 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 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. Enumerating all entries in a map is accomplished with the function.
The function 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. The function can be used like any
other YP procedure, to identify the map in the normal manner, and to supply the name of a function that will be called to process each key-
value pair within the map. Returns from the call to occur only when the transaction is completed (successfully or unsuccessfully), or when
the function decides that it does not want to see any more key-value pairs.
The third parameter to is
struct ypall_callback *incallback {
int (*foreach)();
char *data;
};
The function 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 that converts a YP protocol error code to a ypclnt layer error code.)
The key and value parameters are somewhat different than defined in the syntax section above. First, the memory pointed to by the inkey
and inval parameters is private to the function and is overwritten with the arrival of each new key-value pair. It is the responsibility
of the function to do something useful with the contents of that memory, but it does not own the memory itself. Key and value objects pre-
sented to the 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 The data element of the callback structure may be used to
share state information between the function and the mainline code. Its use is optional, and no part of the YP client package inspects its
contents.
The function returns a Boolean value. It should return zero to indicate that it wants to be called again for further received key-value
pairs, or nonzero to stop the flow of key-value pairs. If returns a nonzero value, it is not called again; the functional value of is then
0.
The function returns the order number for a map.
The function returns the machine name of the master YP server for a map.
The function returns a pointer to an error message string that is null-terminated but contains no period or new line.
The function 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
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 /* can't 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 yp 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 /* can't communicate with portmapper */
#define YPERR_YPBIND 10 /* can't communicate with ypbind */
#define YPERR_YPSERV 11 /* can't communicate with ypserv */
#define YPERR_NODOM 12 /* local domain name not set */
Files
/usr/include/rpcsvc/ypclnt.h
/usr/include/rpcsvc/yp_prot.h
See Also
ypfiles(5yp), ypserv(8yp)
ypclnt(3yp)