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yp_first(3c)
Standard C Library Functions ypclnt(3C)
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
#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, intinkeylen,
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(int 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 Oracle Solaris, NIS version 2 is supported only for compatibility
with previous versions. The current Oracle Solaris operating system
supports the client interface to NIS version 2. This client interface
will be served by an existing ypserv process running on another machine
on the network. For commands used to access NIS from a client machine,
see ypbind(8), ypwhich(1), ypmatch(1), and ypcat(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 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 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 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 indo‐
main parameter to successive NIS name service calls. The domain
returned is the same as that returned using the SI_SRPC_DOMAIN com‐
mand 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 avail‐
able. 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 ini‐
tial 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 + sec‐
ond 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, val‐
ues, 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 database 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 iden‐
tify the map in the normal manner and to supply the name of a func‐
tion that will be called to process each key-value pair within the
map. The call to yp_all() returns only when the transaction is com‐
pleted (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 pro‐
tocol 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 ele‐
ment passed to yp_all(). The data element of the callback structure
can be used to share state information between the foreach() func‐
tion and the mainline code. Its use is optional, and no part of the
NIS client package inspects its contents; cast it to something use‐
ful, 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 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.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ MT-LevelSafe
SEE ALSO
ypcat(1), ypmatch(1), ypwhich(1), sysinfo(2), malloc(3C), ypfiles(5),
attributes(7), rpcbind(8), ypbind(8), ypserv(8)
Oracle Solaris 11.4 11 May 2021 ypclnt(3C)