ypclnt(3N) 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 com-
mands 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 unini-
tialized character pointers. Memory is allocated by the YP client
package using malloc(), and may be freed if the user code has no con-
tinuing need for it. For each outkey and outval, two extra bytes of
memory are allocated 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-termi-
nated. String parameters which are accompanied by a count parameter
may not be NULL, but may point to NULL strings, with the count parame-
ter 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
int ypbind(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 ser-
vices are not available.
void ypunbind(char *indomain);
Each binding allocates (uses up) one client process socket
descriptor; each bound domain costs one socket descriptor. How-
ever, multiple requests to the same domain use that same descrip-
tor. ypunbind() is available at the client interface for
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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
- 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.
int ypgetdefaultdomain(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
name service calls.
int ypmatch(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.
int ypfirst(char *indomain, char *inmap, char **outkey,
int *outkeylen, char **outval, int *outvallen);
ypfirst() returns the first key-value pair from the named map in
the named domain.
int ypnext(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).
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The concept of first (and, for that matter, of next) is particu-
lar 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 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() func-
tion is called on a particular map, and then the ypnext() func-
tion 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 oth-
erwise be returned in the midst of the enumeration. The next
paragraph describes a better solution to enumerating all entries
in a map.
int ypall(char *indomain, char *inmap,
struct ypallcallback *incallback);
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 normal 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 unsuccessfully), 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;
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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() func-
tion, 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 ele-
ment passed to ypall(). The data element of the callback struc-
ture 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 some-
thing useful, or ignore it.
The foreach function is a Boolean. It should return zero to indi-
cate 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.
int yporder(char *indomain, char *inmap, int *outorder);
yporder() returns the order number for a map.
int ypmaster(char *indomain, char *inmap, char **outname);
ypmaster() returns the machine name of the master YP server for
a map.
char *yperrstring(int incode);
yperrstring() returns a pointer to an error message string that
is NULL-terminated but contains no period or NEWLINE.
int ypproterr(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().
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DIAGNOSTICS
All integer functions return 0 if the requested operation is success-
ful, or one of the following errors if the operation fails.
1 args to function are bad
2 RPC failure - domain has been unbound
3 can't bind to server on this domain
4 no such map in server's domain
5 no such key in map
6 internal yp server or client error
7 resource allocation failure
8 no more records in map database
9 can't communicate with rpcbinder
10 can't communicate with ypbind
11 can't communicate with ypserv
12 local domain name not set
13 yp database is bad
14 yp version mismatch
15 access violation
16 database busy
FILES
/usr/lib/libyp.a
SEE ALSO
ypserv(1M), malloc(3C), ypupdate(3N), malloc(3X), ypfiles(4).
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