Tribblix: manual page: ypclnt.3nsl

YPCLNT(3NSL) Networking Services Library Functions 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
Information Service Version 2, formerly referred to as YP. For
commands used to access NIS from a client machine, see ypbind(8),
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
uninitialized 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, 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 may not be null, but they 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.
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
explicitly by user code. Binding is done
automatically 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 available. 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, multiple requests to the same
domain use that same descriptor. The
yp_unbind() function is available at the
client interface for processes 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
automatically. At that point, the ypclnt()
layer will retry a few more times or until
the operation succeeds, provided that
rpcbind(8) and ypbind(8) 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 indomain
parameter to successive NIS name service
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
parameter must 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). 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 processed. 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 ordering 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 package). 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() 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:

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
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. 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-terminated 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 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 Boolean. 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 foreach() 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.

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
successful, 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