ypclnt(3N) 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 - NIS client interface
SYNOPSIS
cc [options] file -lnsl
#include <rpcsvc/ypclnt.h>
#include <rpcsvc/yp_prot.h>
int yp_bind (char *indomain);
void yp_unbind (char *indomain);
int yp_get_default_domain (char **outdomain);
int yp_match(char *indomain, char *inmap, char *inkey, int inkeylen,
char **outval, int *outvallen);
int yp_first(char *indomain, char *inmap, char **outkey, int *outkeylen,
char **outval, int *outvallen);
int yp_next(char *indomain, char *inmap, char *inkey, int inkeylen,
char **outkey, int *outkeylen, char **outval, int *outvallen);
int yp_all(char *indomain, char *inmap, struct ypall_callback *incallback);
int yp_order(char *indomain, char *inmap, int *outorder);
int yp_master(char *indomain, char *inmap, char **outname);
const char *yperr_string(int incode);
int ypprot_err (unsigned int incode);
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. 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 parameter 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(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.
Copyright 1994 Novell, Inc. Page 1
ypclnt(3N) ypclnt(3N)
All functions in this package of type int return 0 if they
succeed, and a failure code (YPERR_xxxx) otherwise. Functions
requiring a full YP map name cannot use nicknames. For
example, hosts.byname must be used instead of the nickname
hosts. Failure codes are described under Return Values below.
Routines
int
yp_bind (char *indomain);
To use the NIS name services, the client process must be
bound to a NIS server that serves the appropriate domain
using yp_bind. Binding need not be done explicitly by
user code; this is done automatically whenever a NIS
lookup function is called. yp_bind 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
yp_unbind (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. yp_unbind is available
at the client interface for processes that explicitly
manage their socket descriptors while accessing multiple
domains. The call to yp_unbind 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.
Copyright 1994 Novell, Inc. Page 2
ypclnt(3N) ypclnt(3N)
int
yp_get_default_domain (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
yp_get_default_domain, and use the returned outdomain as
the indomain parameter to successive NIS name service
calls.
int
yp_match(char *indomain, char *inmap, char *inkey, int inkeylen,
char **outval, int *outvallen);
yp_match returns the value associated with a passed key.
This key must be exact; no pattern matching is
available.
int
yp_first(char *indomain, char *inmap, char **outkey, int *outkeylen,
char **outval, int *outvallen);
yp_first returns the first key-value pair from the named
map in the named domain.
int
yp_next(char *indomain, char *inmap, char *inkey, int inkeylen,
char **outkey, int *outkeylen, char **outval, int *outvallen);
yp_next returns the next key-value pair in a named map.
The inkey parameter should be the outkey returned from
an initial call to yp_first (to get the second key-value
pair) or the one returned from the nth call to yp_next
(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 yp_first
function is called on a particular map, and then the
yp_next function is repeatedly called on the same map at
the same server until the call fails with a reason of
Copyright 1994 Novell, Inc. Page 3
ypclnt(3N) ypclnt(3N)
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. The next
paragraph describes a better solution to enumerating all
entries in a map.
int
yp_all(char *indomain, char *inmap, struct ypall_callback *incallback);
yp_all 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. yp_all 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 yp_all 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 yp_all is
struct ypall_callback *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/yp_prot.h-either YP_TRUE
or an error code. (See ypprot_err, below, for a function
which converts a NIS name service protocol error code to
Copyright 1994 Novell, Inc. Page 4
ypclnt(3N) ypclnt(3N)
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 yp_all 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 yp_all. 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 yp_all is then 0.
int
yp_order(char *indomain, char *inmap, int *outorder);
yp_order returns the order number for a map.
int
yp_master(char *indomain, char *inmap, char **outname);
yp_master returns the machine name of the master NIS
server for a map.
const
char *yperr_string(int incode);
Copyright 1994 Novell, Inc. Page 5
ypclnt(3N) ypclnt(3N)
yperr_string returns a pointer to a read-only error
message string that is NULL-terminated but contains no
period or newline.
int
ypprot_err (unsigned int incode);
ypprot_err 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 yperr_string.
Files
/usr/lib/libnsl.so
Return Values
All integer functions return 0 if the requested operation is
successful, or one of the following errors if the operation
fails.
1 YPERR_BADARGS args to function are bad
2 YPERR_RPC RPC failure - domain has been unbound
3 YPERR_DOMAIN can't bind to server on this domain
4 YPERR_MAP no such map in server's domain
5 YPERR_KEY no such key in map
6 YPERR_YPERR internal NIS server or client error
7 YPERR_RESRC resource allocation failure
8 YPERR_NOMORE no more records in map database
9 YPERR_PMAP can't communicate with RPC binder
10 YPERR_YPBIND can't communicate with ypbind
11 YPERR_YPSERV can't communicate with ypserv
12 YPERR_NODOM local domain name not set
13 YPERR_BADDB NIS database is bad
14 YPERR_VERS NIS version mismatch
15 YPERR_ACCESS access violation
16 YPERR_BUSY database busy
REFERENCES
malloc(3C), ypfiles(4), ypserv(1M), ypupdate(3N)
Copyright 1994 Novell, Inc. Page 6