ypclnt(3N) UNIX System V ypclnt(3N)
NAME
ypclnt, ypgetdefaultdomain, ypbind, ypunbind, ypmatch, ypfirst,
ypnext, ypall, yporder, ypmaster, yperrstring, ypproterr - NIS
client interface
SYNOPSIS
#include <rpcsvc/ypclnt.h>
#include <rpcsvc/ypprot.h>
DESCRIPTION
This package of functions provides an interface to the NIS 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 NIS name services, including the definitions of map and
domain, and a description of the various servers, databases, and commands
that comprise the NIS 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 NIS client
package using malloc(3), 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 (ERRxxxx) otherwise. Failure codes are described under
DIAGNOSTICS below.
Routines
int ypbind (char *indomain);
To use the NIS name services, the client process must be bound to a
NIS server that serves the appropriate domain using ypbind.
Binding need not be done explicitly by user code; this is done
automatically whenever a NIS 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 NIS services are
not available.
void ypunbind (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 available at the client interface for
processes that explicitly manage their socket descriptors while
accessing multiple domains. The call to ypunbind make the domain
10/89 Page 1
ypclnt(3N) UNIX System V ypclnt(3N)
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 NIS 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 NIS 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).
The concept of first (and, for that matter, of next) is particular
to the structure of the NIS map being processing; there is no
relation in retrieval order to either the lexical order within any
original (non-NIS 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
Page 2 10/89
ypclnt(3N) UNIX System V ypclnt(3N)
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.
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 NIS 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
int foreach(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 NIS 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
10/89 Page 3
ypclnt(3N) UNIX System V ypclnt(3N)
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 NIS client package inspects its contents-cast it to
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.
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 NIS 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 NIS 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.
Page 4 10/89
ypclnt(3N) UNIX System V ypclnt(3N)
1 YPERRBADARGS args to function are bad
2 YPERRRPC RPC failure - domain has been unbound
3 YPERRDOMAIN can't bind to server on this domain
4 YPERRMAP no such map in server's domain
5 YPERRKEY no such key in map
6 YPERRYPERR internal NIS server or client error
7 YPERRRESRC resource allocation failure
8 YPERRNOMORE no more records in map database
9 YPERRPMAP can't communicate with RPC binder
10 YPERRYPBIND can't communicate with ypbind
11 YPERRYPSERV can't communicate with ypserv
12 YPERRNODOM local domain name not set
13 YPERRBADDB NIS database is bad
14 YPERRVERS NIS version mismatch
15 YPERRACCESS access violation
16 YPERRBUSY database busy
10/89 Page 5