YPCLNT(3)               NetBSD Library Functions Manual              YPCLNT(3)

NAME
     yp_all, yp_bind, yp_first, yp_get_default_domain, yp_master, yp_match,
     yp_next, yp_order, yp_unbind, yperr_string, ypprot_err yp_setbindtries --
     Interface to the YP subsystem

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/types.h>
     #include <rpc/rpc.h>
     #include <rpcsvc/ypclnt.h>
     #include <rpcsvc/yp_prot.h>

     int
     yp_all(const char *indomain, const char *inmap,
         struct ypall_callback *incallback);

     int
     yp_bind(const char *dom);

     int
     yp_first(const char *indomain, const char *inmap, char **outkey,
         int *outkeylen, char **outval, int *outvallen);

     int
     yp_get_default_domain(char **outdomain);

     int
     yp_master(const char *indomain, const char *inmap, char **outname);

     int
     yp_match(const char *indomain, const char *inmap, const char *inkey,
         int inkeylen, char **outval, int *outvallen);

     int
     yp_next(const char *indomain, const char *inmap, const char *inkey,
         int inkeylen, char **outkey, int *outkeylen, char **outval,
         int *outvallen);

     int
     yp_order(const char *indomain, const char *inmap, int *outorder);

     void
     yp_unbind(const char *dom);

     char *
     yperr_string(int incode);

     int
     ypprot_err(unsigned int incode);

     int
     yp_setbindtries(int ntries);

DESCRIPTION
     The ypclnt suite provides an interface to the YP subsystem.  For a gen-
     eral description of the YP subsystem, see yp(8).

     For all functions, input values begin with in and output values begin
     with out.

     Any output values of type char ** should be the addresses of uninitial-
     ized character pointers.  These values will be reset to the null pointer
     (unless the address itself is the null pointer, in which case the error
     YPERR_BADARGS will be returned).  If necessary, memory will be allocated
     by the YP client routines using malloc(), and the result will be stored
     in the appropriate output value.  If the invocation of a YP client rou-
     tine doesn't return an error, and an output value is not the null
     pointer, then this memory should be freed by the user when there is no
     additional need for the data stored there.  For outkey and outval, two
     extra bytes of memory are allocated for a `\n' and `\0', which are not
     reflected in the values of outkeylen or outvallen.

     All occurrences of indomain and inmap must be non-null, NUL-terminated
     strings.  All input strings which also have a corresponding length param-
     eter cannot be the null pointer unless the corresponding length value is
     zero.  Such strings need not be NUL-terminated.

     All YP lookup calls (the functions yp_all(), yp_first(), yp_master(),
     yp_match(), yp_next(), yp_order()) require a YP domain name and a YP map
     name.  The default domain name may be obtained by calling
     yp_get_default_domain(), and should thus be used before all other YP
     calls in a client program.  The value it places outdomain is suitable for
     use as the indomain parameter to all subsequent YP calls.

     In order for YP lookup calls to succeed, the client process must be bound
     to a YP server process.  The client process need not explicitly bind to
     the server, as it happens automatically whenever a lookup occurs.  The
     function yp_bind() is provided for a backup strategy, e.g. a local file,
     when a YP server process is not available.  Each binding uses one socket
     descriptor on the client process, which may be explicitly freed using
     yp_unbind(), which frees all per-process and per-node resources to bind
     the domain and marks the domain unbound.

     If, during a YP lookup, an RPC failure occurs, the domain used in the
     lookup is automatically marked unbound and the ypclnt layer retries the
     lookup as long as ypbind(8) is running and either the client process can-
     not bind to a server for the domain specified in the lookup, or RPC
     requests to the YP server process fail.  If an error is not RPC-related,
     one of the YP error codes described below is returned and control given
     back to the user code.

     The ypclnt suite provides the following functionality:

     yp_match()    Provides the value associated with the given key.

     yp_first()    Provides the first key-value pair from the given map in the
                   named domain.

     yp_next()     Provides the next key-value pair in the given map.  To
                   obtain the second pair, the inkey value should be the
                   outkey value provided by the initial call to yp_first().
                   In the general case, the next key-value pair may be
                   obtained by using the outkey value from the previous call
                   to yp_next() as the value for inkey.

                   Of course, the notions of ``first'' and ``next'' are par-
                   ticular to the type of YP map being accessed, and thus
                   there is no guarantee of lexical order.  The only guaran-
                   tees provided with yp_first() and yp_next(), providing that
                   the same map on the same server is polled repeatedly until
                   yp_next() returns YPERR_NOMORE, are that all key-value
                   pairs in that map will be accessed exactly once, and if the
                   entire procedure is repeated, the order will be the same.

                   If the server is heavily loaded or the server fails for
                   some reason, the domain being used may become unbound.  If
                   this happens, and the client process re-binds, the
                   retrieval rules will break: some entries may be seen twice,
                   and others not at all.  For this reason, the function
                   yp_all() provides a better solution for reading all of the
                   entries in a particular map.

     yp_all()      This function provides a way to transfer an entire map from
                   the server to the client process with a single request.
                   This transfer uses TCP, unlike all other functions in the
                   ypclnt suite, which use UDP.  The entire transaction occurs
                   in a single RPC request-response.  The third argument to
                   this function provides a way to supply the name of a func-
                   tion to process each key-value pair in the map.  yp_all()
                   returns after the entire transaction is complete, or the
                   foreach function decides that it does not want any more
                   key-value pairs.  The third argument to yp_all() is:

                         struct ypall_callback *incallback {
                                 int (*foreach)();
                                 char *data;
                         };

                   The char *data argument is an opaque pointer for use by the
                   callback function.  The foreach function should return non-
                   zero when it no longer wishes to process key-value pairs,
                   at which time yp_all() returns a value of 0, and is called
                   with the following arguments:

                         int foreach (
                                 int instatus,
                                 char *inkey,
                                 int inkeylen,
                                 char *inval,
                                 int invallen,
                                 char *indata
                         );

                   Where:

                   instatus      Holds one of the return status values
                                 described in <rpcsvc/yp_prot.h>: see
                                 ypprot_err() below for a function that will
                                 translate YP protocol errors into a ypclnt
                                 layer error code as described in
                                 <rpcsvc/ypclnt.h>.

                   inkey, inval  The key and value arguments are somewhat dif-
                                 ferent here than described above.  In this
                                 case, the memory pointed to by inkey and
                                 inval is private to yp_all(), and is over-
                                 written with each subsequent key-value pair,
                                 thus the foreach function should do something
                                 useful with the contents of that memory dur-
                                 ing each iteration.  If the key-value pairs
                                 are not terminated with either `\n' or `\0'
                                 in the map, then they will not be terminated
                                 as such when given to the foreach function,
                                 either.

                   indata        This is the contents of the incallback->data
                                 element of the callback structure.  It is
                                 provided as a means to share state between
                                 the foreach function and the user code.  Its
                                 use is completely optional: cast it to some-
                                 thing useful or simply ignore it.

     yp_order()    Returns the order number for a map.

     yp_master()   Returns the hostname for the machine on which the master YP
                   server process for a map is running.

     yperr_string()
                   Returns a pointer to a NUL-terminated error string that
                   does not contain a `.' or `\n'.

     ypprot_err()  Converts a YP protocol error code to a ypclnt error code
                   suitable for yperr_string().

     yp_setbindtries()
                   Set the number of tries to attempt to bind to the domain
                   before returning an error.  The default is 0 which means
                   wait forever if no ypserver is not found of if the RPC com-
                   munication with the yp server fails.  If the number passed
                   is negative, the current number of tries is not modified.

                   This function is an extention to the client library that
                   allows application to catch communication problems with the
                   ypserver without blocking forever.

RETURN VALUES
     All functions in the ypclnt suite which are of type int return 0 upon
     success or one of the following error codes upon failure:

     [YPERR_BADARGS]   The passed arguments to the function are invalid.

     [YPERR_BADDB]     The YP map that was polled is defective.

     [YPERR_DOMAIN]    Client process cannot bind to server on this YP domain.

     [YPERR_KEY]       The key passed does not exist.

     [YPERR_MAP]       There is no such map in the server's domain.

     [YPERR_DOM]       The local YP domain is not set.

     [YPERR_NOMORE]    There are no more records in the queried map.

     [YPERR_PMAP]      Cannot communicate with portmapper (see rpcbind(8)).

     [YPERR_RESRC]     A resource allocation failure occurred.

     [YPERR_RPC]       An RPC failure has occurred.  The domain has been
                       marked unbound.

     [YPERR_VERS]      Client/server version mismatch.  If the server is run-
                       ning version 1 of the YP protocol, yp_all() functional-
                       ity does not exist.

     [YPERR_BIND]      Cannot communicate with ypbind(8).

     [YPERR_YPERR]     An internal server or client error has occurred.

     [YPERR_YPSERV]    The client cannot communicate with the YP server
                       process.

SEE ALSO
     malloc(3), yp(8), ypbind(8), ypserv(8)

AUTHORS
     Theo De Raadt

NetBSD 7.0                       March 2, 2012                      NetBSD 7.0

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