ypclnt(NS) 6 January 1993 ypclnt(NS) Name ypclnt - Network Information Service (NIS) client interface Syntax #include <rpcsvc/ypclnt.h> yp_bind(indomain) char *indomain; void yp_unbind(indomain) char *indomain; yp_get_default_domain(outdomain) char **outdomain; yp_match(indomain, inmap, inkey, inkeylen, outval, outvallen) char *indomain; char *inmap; char *inkey; int inkeylen; char **outval; int *outvallen; yp_first(indomain, inmap, outkey, outkeylen, outval, outvallen) char *indomain; char *inmap; char **outkey; int *outkeylen; char **outval; int *outvallen; yp_next(indomain, inmap, inkey, inkeylen, outkey, outkeylen, outval, outvallen) char *indomain; char *inmap; char *inkey; int inkeylen; char **outkey; int *outkeylen; char **outval; int *outvallen; yp_all(indomain, inmap, incallback) char *indomain; char *inmap; struct ypall_callback incallback; yp_order(indomain, inmap, outorder) char *indomain; char *inmap; int *outorder; yp_master(indomain, inmap, outname) char *indomain; char *inmap; char **outname; char *yperr_string(incode) int incode; ypprot_err(incode) unsigned int incode; Description This package of functions provides an interface to the Network Informa- tion Service (NIS) network lookup service. The package can be loaded from the standard library, /usr/lib/libyp.a. The RPC library, /usr/lib/librpc.a, and the transport library will probably need to be linked in as well. Refer to ypfiles(NF) and ypserv(NADM) for an overview of the Network Information Service, including the definitions of map and domain, as well as a description of the various servers, databases, and commands that comprise the NIS. All input parameters names begin with in. Output parameters begin with out. Output parameters of type char ** should be addresses of uninitial- ized character pointers. Memory is allocated by the NIS client package using malloc(S), and may be freed if the user code has no continuing need for it. For each outkey and outval, two extra bytes of memory are allo- cated at the end that contain NEWLINE and NULL, respectively, but these two bytes are not reflected in outkeylen or outvallen. indomain and inmap strings must be non-null and null-terminated. String parameters which are accompanied by a count parameter may not be null, but 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 zero if they succeed and a failure code (YPERR_xxxx) otherwise. These failure codes are described under ``Diagnostics'' below. The NIS lookup calls require at least a map name and a domain name. It is assumed that the client process knows the name of the map of interest. Client processes should fetch the node's default domain by calling ypgetdefaultdomain() and use the returned outdomain as the indomain parameter to successive NIS calls. To use the NIS services, the client process must be ``bound'' to a NIS server that serves the appropriate domain using ypbind. Binding need not be done explicitly by user code; this is done automatically whenever a NIS lookup function is called. ypbind can be called directly for pro- cesses that make use of a backup strategy (for example, a local file) in cases when NIS services are not available. Each binding allocates (uses up) one client process socket descriptor; each bound domain costs one socket descriptor. However, multiple requests to the same domain use the same descriptor. ypunbind() is available at the client interface for processes that explicitly manage their socket descriptors while accessing multiple domains. The call to ypunbind() make the domain unbound and free 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 for- ever or until the operation succeeds, provided that ypbind is running and either: + the client process cannot bind a server for the proper domain, or + RPC requests to the server fail. If an error is not RPC-related, or if ypbind is not running, or if a bound ypserv process returns any answer (success or failure), the ypclnt layer will return control to the user code, either with an error code, or a success code and any results. ypmatch returns the value associated with a passed key. This key must be exact; no pattern matching is available. ypfirst returns the first key-value pair from the named map in the named domain. ypnext() returns the next key-value pair in a named map. The inkey parameter should be the outkey returned from an initial call to ypfirst() (to get the second key-value pair) or the one returned from the nth call to ypnext() (to get the nth + second key-value pair). The concept of first and next is particular to the structure of the NIS map being processing; 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 ypfirst() function is called on a particular map and then the ypnext() function is called repeatedly 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 mes- sages that would otherwise be returned in the midst of the enumeration. The next paragraph describes a better solution to enumerating all entries in a map. ypall 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. You can use ypall just like any other NIS procedure, identify the map in the normal manner, and supply the name of a function which will be called to process each key-value pair within the map. You return from the call to ypall only when the transaction is completed (successfully or unsuccessfully), or your foreach function decides that it does not want to see any more key-value pairs. The third parameter to ypall is struct ypall_callback *incallback { int (*foreach)(); char *data; }; The function foreach is called foreach(instatus, inkey, inkeylen, inval, invallen, indata) int instatus; char *inkey; int inkeylen; char *inval; int invallen; char *indata; The instatus parameter will hold one of the return status values defined in <rpcsvc/yp_prot.h> -- either YP_TRUE or an error code. (See ypproterr, below, for a function which 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 to which the inkey and inval pa- rameters points is private to the ypall 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. The 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 ypall. 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 is a Boolean. It should return zero 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 ypall is then 0. yporder returns the order number for a map. ypmaster returns the machine name of the master NIS server for a map. yperrstring returns a pointer to an error message string that is null- terminated but contains no period or newline. ypproterr 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 yperrstring. Files /usr/include/rpcsvc/ypclnt.h /usr/include/rpcsvc/yp_prot.h See also ypfiles(NF) and ypserv(NADM). Diagnostics 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 /* cannot 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 NIS 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 /* cannot communicate with portmapper */ #define YPERR_YPBIND 10 /* cannot communicate with ypbind */ #define YPERR_YPSERV 11 /* cannot communicate with ypserv */ #define YPERR_NODOM 12 /* local domain name not set */ #define YPERR_BADDB 13 /* NIS data base is bad */ #define YPERR_VERS 14 /* NIS version mismatch */