yp_get_default_domain, yp_bind, yp_unbind, yp_match,
yp_first, yp_next, yp_all, yp_order, yp_master,
yperr_string, ypprot_err - Network Information Service
(NIS) client package
#include <rpcsvc/ypclnt.h>
int yp_get_default_domain(
char **outdomain ); int ypbind(
char *indomain ); int yp_unbind(
char *indomain ); 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 ypcallback incallback ); int yp_order(
char *indomain,
char *inmap,
int *outorder ); int yp_master(
char *indomain,
char *inmap,
char **outname ); char *yperr_string(
int incode ); char ypprot_err(
unsigned int incode );
This package of functions provides an interface to the
Network Information Service (NIS) database lookup service.
The package can be loaded from the standard library,
/lib/libc.a. Refer to ypfiles(4) and ypserv(8) for an
overview of NIS, including the definitions of "map" and
"domain", and for a description of the servers, data
bases, and commands that constitute the NIS application.
All input parameters names begin with "in". Output parameters
begin with "out". Output parameters of type char **
should be addresses of uninitialized character pointers.
The NIS client package allocates memory using malloc(3).
This memory can be freed if the user code has no continuing
need for it. The yp_get_default_domain() function,
however, returns a pointer to thread-specific data. Therefore,
the memory cannot be freed by user code. (The
contents of that memory are updated with the current
default domain on each call.)
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 cannot be null,
but can point to null strings, with the count parameter
indicating this. Counted strings need not be null-terminated.
All functions of type int return 0 if they succeed, or a
failure code (YPERR_xxxx) if they do not succeed. Failure
codes are described in the ERRORS section of this reference
page.
The NIS lookup calls require a map name and a domain name.
It is assumed that the client thread knows the name of the
map of interest. Client threads fetch the node's default
domain by calling yp_get_default_domain(), and use the
returned outdomain as the indomain parameter to successive
NIS calls.
To use NIS services, the client thread must be bound to a
NIS server that serves the appropriate domain. The binding
is accomplished with yp_bind(). Binding need not be done
explicitly by user code; it is done automatically whenever
a NIS lookup function is called. The yp_bind() function
can be called directly for processes that make use of a
backup strategy in cases when NIS services are not available.
Each binding allocates one client process socket descriptor;
each bound domain in each thread requires one socket
descriptor. Multiple requests to the same domain from the
same thread use that same descriptor. The yp_unbind()
function is available at the client interface for threads
that explicitly manage their socket descriptors while
accessing multiple domains. The call to yp_unbind() makes
the domain unbound, and frees all per-thread and per-node
resources used to bind it.
If an RPC failure results upon use of a binding, that
domain will be unbound automatically for the thread that
encountered the error. At that point, the ypclnt layer
will retry forever or until the operation succeeds. This
action occurs provided that ypbind is running, and either
the client thread cannot bind a server for the proper
domain, or RPC requests to the server fail.
The ypbind -S option allows the system administrator to
lock ypbind to a particular domain and set of servers. Up
to four servers can be specified. An example of the -S
option follows:
/usr/sbin/ypbind -S
domain,server1[,server2,server3,server4]
The ypclnt layer will return control to the user code,
either with an error code, or with a success code and any
results under certain circumstances. For example, control
will be returned to the user code when an error is not
RPC-related and also when the ypbind() function is not
running. An additional situation that will cause the
return of control is when a bound ypserv process returns
any answer (success or failure).
The yp_match() function returns the value associated with
a passed key. This key must be exact; no pattern matching
is available.
The yp_first() function returns the first key-value pair
from the named map in the named domain.
The yp_next() function 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 of next is particular to the
structure of the NIS map being processed; there is no
relation in retrieval order to either the lexical order
within any original (non-NIS) 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 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. Enumerating all
entries in a map is accomplished with the yp_all() function.
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 take place as a single RPC request
and response. The yp_all() function can be used like any
other NIS 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.
Returns from the call to yp_all() occur only when the
transaction is completed (successfully or unsuccessfully),
or when the foreach() function decides that it does not
want to see any more key-value pairs.
The third parameter to yp_all() is as follows:
struct ypall_callback *incallback {
int (*foreach)();
char *data; };
The foreach() function is defined as follows: foreach(
int instatus,
char *inkey,
int intkeylen,
char *inval,
int invallen,
char *indata );
The instatus parameter will hold one of the return status
values defined in the rpcsvc/yp_prot.h header file -
either YP_TRUE or an error code. (See the discussion of
ypprot_err() for a function that converts a NIS protocol
error code to a ypclnt layer error code.)
The key and value parameters are somewhat different than
defined in the syntax 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.
The foreach() function returns a Boolean value. It should
return zero to indicate that it wants to be called again
for further received key-value pairs, or nonzero to stop
the flow of key-value pairs. If foreach() returns a
nonzero value, it is not called again; the functional
value of yp_all is then 0.
The yp_order() function returns the order number for a
map.
The yp_master() function returns the machine name of the
master NIS server for a map.
The yperr_string() function returns a pointer to an error
message string that is null-terminated but contains no
period or new line.
The ypprot_err() function takes a NIS protocol error code
as input and returns a ypclnt layer error code, which may
be used in turn as an input to yperr_string().
All integer functions return 0 if the requested operation
is successful, or one of the following errors if the operation
fails:
#define YPERR_BADARGS 1 /* args to function are bad */
#define YPERR_RPC 2 /* RPC failure - domain has been
unbound */ #define YPERR_DOMAIN 3 /* can't bind to server
on this domain */ #define YPERR_MAP 4 /* no such map in
server's domain */ #define YPERR_KEY 5 /* no such key in
map */ #define YPERR_YPERR 6 /* internal yp server or
client error */ #define YPERR_RESRC 7 /* resource allocation
failure */ #define YPERR_NOMORE 8 /* no more records
in map database */ #define YPERR_PMAP 9 /* can't communicate
with portmapper */ #define YPERR_YPBIND 10 /* can't
communicate with ypbind */ #define YPERR_YPSERV 11 /*
can't communicate with ypserv */ #define YPERR_NODOM 12 /*
local domain name not set */
Header file containing ypclnt definitions. Header file
defining return status values.
Commands: ypserv(8)
Files: ypfiles(4)
ypclnt(3)
[ Back ] |
