YPCLNT(3NSL)YPCLNT(3NSL)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
Version 2 client interface
SYNOPSIS
cc [ -flag... ] file... -lnsl [ library...]
#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 *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, unsigned long *outorder);
int yp_master(char *indomain, char *inmap, char **outname);
char *yperr_string(int incode);
int ypprot_err(char *domain);
DESCRIPTION
This package of functions provides an interface to NIS, Network Infor‐
mation Service Version 2, formerly referred to as YP. In this version
of SunOS, NIS version 2 is supported only for compatibility with previ‐
ous versions. The recommended enterprise level information service is
NIS+ or NIS version 3. See NIS+(1). The current SunOS supports only the
client interface to NIS version 2. This client interface will in turn
be served either by an existing ypserv process running on another
machine on the network that has an earlier version of SunOS, or by a
NIS+ server running in "YP-compatibility mode". See rpc.nisd(1M). The
NOTES section in ypfiles(4) discusses the implications of being an NIS
client of an NIS+ server in YP-compatibility mode. For commands used to
access NIS from a client machine, see ypbind(1M), ypwhich(1),
ypmatch(1), and ypcat(1). The package can be loaded from the standard
library, /usr/lib/libnsl.so.1.
All input parameter 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 NIS client
package using malloc(3C) and can be freed by the user code if it 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, respec‐
tively, but these two bytes are not reflected in outkeylen or out‐
vallen. The indomain and inmap strings must be non-null and null-termi‐
nated. String parameters that are accompanied by a count parameter may
not be null, but they 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.
Otherwise, they return a failure code (YPERR_xxxx). Failure codes are
described in the ERRORS section.
Routines
yp_bind()
To use the NIS name services, the client
process must be "bound" to an NIS server
that serves the appropriate domain using
yp_bind(). Binding need not be done explic‐
itly by user code. Binding is done automati‐
cally whenever an NIS lookup function is
called. The yp_bind() function 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 avail‐
able. A process should call yp_unbind() when
it is finished using NIS in order to free up
resources.
yp_unbind()
Each binding allocates or uses up one client
process socket descriptor. Each bound domain
costs one socket descriptor. However, multi‐
ple requests to the same domain use that
same descriptor. The yp_unbind() function is
available at the client interface for pro‐
cesses that explicitly manage their socket
descriptors while accessing multiple
domains. The call to yp_unbind() 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 auto‐
matically. At that point, the ypclnt() layer
will retry a few more times or until the
operation succeeds, provided that
rpcbind(1M) and ypbind(1M) are running, and
either:
o The client process cannot bind a
server for the proper domain; or
o RPC requests to the server fail.
Under the following circumstances, the
ypclnt layer will return control to the user
code, with either an error or success code
and the results:
o If an error is not RPC-related.
o If rpcbind is not running.
o If ypbind is not running.
o If a bound ypserv process returns
any answer (success or failure).
yp_get_default_domain()
NIS lookup calls require a map name and a
domain name, at minimum. The client process
should know the name of the map of interest.
Client processes fetch the node's default
domain by calling yp_get_default_domain()
and use the returned outdomain as the indo‐
main parameter to successive NIS name ser‐
vice calls. The domain returned is the same
as that returned using the SI_SRPC_DOMAIN
command to the sysinfo(2) system call. The
value returned in outdomain should not be
freed.
yp_match()
The yp_match() function returns the value
associated with a passed key. This key must
be exact because no pattern matching is
available. yp_match() requires a full YP
map name, such as hosts.byname, instead of
the nickname hosts.
yp_first()
The yp_first() function returns the first
key-value pair from the named map in the
named domain.
yp_next()
The yp_next() function returns the next key-
value pair in a named map. The inkey param‐
eter must be the outkey returned from an
initial call to yp_first() (to get the sec‐
ond key-value pair) or the one returned from
the nth call to yp_next() (to get the nth +
second key-value pair). Similarly, the
inkeylen parameter must be the outkeylen
returned from the earlier yp_first() or
yp_next() call.
The concept of first and next is particular
to the structure of the NIS map being pro‐
cessed. Retrieval order is not related 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 order‐
ing guarantee 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
YPERR_NOMORE, every entry in the data base
is seen exactly once. Further, if the same
sequence of operations is performed on the
same map at the same server, the entries are
seen in the same order.
Under conditions of heavy server load or
server failure, the domain can become
unbound, then bound once again (perhaps to a
different server) while a client is running.
This binding 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. For a better
solution to enumerating all entries in a
map, see yp_all().
yp_all()
The yp_all() 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 pack‐
age). The entire transaction takes place as
a single RPC request and response. The
yp_all() function can be used just like any
other NIS name service 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. The call to yp_all() returns only when
the transaction is completed (successfully
or unsuccessfully), or the foreach() func‐
tion 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:
foreach(int instatus, char *inkey,
int inkeylen, char *inval,
int invallen, char *indata);
The instatus parameter holds one of the
return status values defined in
<rpcsvc/yp_prot.h>, either YP_TRUE or an
error code. See ypprot_err(), for a function
that converts an 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 sec‐
tion 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.
The foreach() function must 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-ter‐
minated or null-terminated in the map, they
would 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
can be used to share state information
between the foreach() function and the main‐
line code. Its use is optional, and no part
of the NIS client package inspects its con‐
tents; cast it to something useful, or
ignore it. The foreach() function is Bool‐
ean. It should return 0 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 fore‐
ach() returns a non-zero value, it is not
called again. The functional value of
yp_all() is then 0.
yp_order()
The yp_order() function returns the order
number for a map. The function is not sup‐
ported if the ypbind process on the client's
system is bound to an NIS+ server running in
"YP-compatibility mode".
yp_master()
The yp_master() function returns the machine
name of the master NIS server for a map.
yperr_string()
The yperr_string() function returns a
pointer to an error message string that is
null-terminated but contains no period or
NEWLINE.
ypprot_err()
The ypprot_err() function takes an NIS name
service protocol error code as input, and
returns a ypclnt() layer error code, which
can be used as an input to yperr_string().
RETURN VALUES
All integer functions return 0 if the requested operation is success‐
ful, or one of the following errors if the operation fails:
YPERR_ACCESS
Access violation.
YPERR_BADARGS
The arguments to the function are bad.
YPERR_BADDB
The YP database is bad.
YPERR_BUSY
The database is busy.
YPERR_DOMAIN
Cannot bind to server on this domain.
YPERR_KEY
No such key in map.
YPERR_MAP
No such map in server's domain.
YPERR_NODOM
Local domain name not set.
YPERR_NOMORE
No more records in map database.
YPERR_PMAP
Cannot communicate with rpcbind.
YPERR_RESRC
Resource allocation failure.
YPERR_RPC
RPC failure; domain has been unbound.
YPERR_YPBIND
Cannot communicate with ypbind.
YPERR_YPERR
Internal YP server or client error.
YPERR_YPSERV
Cannot communicate with ypserv.
YPERR_VERS
YP version mismatch.
FILES
/usr/lib/libnsl.so.1
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│MT-Level │ Safe │
└───────────────┴─────────────────┘
SEE ALSONIS+(1), ypcat(1), ypmatch(1), ypwhich(1), rpc.nisd(1M), rpcbind(1M),
ypbind(1M), ypserv(1M), sysinfo(2), malloc(3C), ypfiles(4),
attributes(5)
Jan 23, 2004 YPCLNT(3NSL)
