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ypclnt(3)
NAME
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
SYNOPSIS
#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 );
DESCRIPTION
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().
ERRORS
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 */
FILES
/usr/include/rpcsvc/ypclnt.h
Header file containing ypclnt definitions.
/usr/include/rpcsvc/yp_prot.h
Header file defining return status values.
SEE ALSO
Commands: ypserv(8)
Files: ypfiles(4)
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