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NSDISPATCH(3)		 BSD Library Functions Manual		 NSDISPATCH(3)

     nsdispatch	-- name-service	switch dispatcher routine

     Standard C	Library	(libc, -lc)

     #include <sys/types.h>
     #include <stdarg.h>
     #include <nsswitch.h>

     nsdispatch(void *retval, const ns_dtab dtab[], const char *database,
	 const char *method_name, const	ns_src defaults[], ...);

     The nsdispatch() function invokes the methods specified in	dtab in	the
     order given by nsswitch.conf(5) for the database database until a suc-
     cessful entry is found.

     retval is passed to each method to	modify as necessary, to	pass back re-
     sults to the caller of nsdispatch().

     Each method has the function signature described by the typedef:

     typedef int (*nss_method)(void *retval, void *mdata, va_list *ap);

     dtab is an	array of ns_dtab structures, which have	the following format:

	   typedef struct _ns_dtab {
		   const char	   *src;
		   nss_method	    method;
		   void		   *mdata;
	   } ns_dtab;

	   The dtab array should consist of one	entry for each source type
	   that	is implemented,	with src as the	name of	the source, method as
	   a function which handles that source, and mdata as a	handle on ar-
	   bitrary data	to be passed to	the method.  The last entry in dtab
	   should contain NULL values for src, method, and mdata.

     Additionally, methods may be implemented in NSS modules, in which case
     they are selected using the database and method_name arguments along with
     the configured source.  (The methods supplied via dtab take priority over
     those implemented in NSS modules in the event of a	conflict.)

     defaults contains a list of default sources to try	if nsswitch.conf(5) is
     missing or	corrupted, or if there is no relevant entry for	database.  It
     is	an array of ns_src structures, which have the following	format:

	   typedef struct _ns_src {
		   const char	   *src;
		   u_int32_t	    flags;
	   } ns_src;

	   The defaults	array should consist of	one entry for each source to
	   be configured by default indicated by src, and flags	set to the
	   criterion desired (usually NS_SUCCESS; refer	to Method return
	   values for more information).  The last entry in defaults should
	   have	src set	to NULL	and flags set to 0.

	   For convenience, a global variable defined as:
		 extern	const ns_src __nsdefaultsrc[];
	   exists which	contains a single default entry	for the	source `files'
	   that	may be used by callers which do	not require complicated	de-
	   fault rules.

     `...' are optional	extra arguments, which are passed to the appropriate
     method as a variable argument list	of the type va_list.

   Valid source	types
     While there is support for	arbitrary sources, the following #defines for
     commonly implemented sources are available:

	   #define	   value
	   NSSRC_FILES	   "files"
	   NSSRC_DNS	   "dns"
	   NSSRC_NIS	   "nis"
	   NSSRC_COMPAT	   "compat"

     Refer to nsswitch.conf(5) for a complete description of what each source
     type is.

   Method return values
     The nss_method functions must return one of the following values depend-
     ing upon status of	the lookup:

     Return value    Status code
     NS_SUCCESS	     success
     NS_NOTFOUND     notfound
     NS_UNAVAIL	     unavail
     NS_TRYAGAIN     tryagain
     NS_RETURN	     -none-

     Refer to nsswitch.conf(5) for a complete description of each status code.

     The nsdispatch() function returns the value of the	method that caused the
     dispatcher	to terminate, or NS_NOTFOUND otherwise.

     hesiod(3),	stdarg(3), nsswitch.conf(5), yp(8)

     The nsdispatch() function first appeared in FreeBSD 5.0.  It was imported
     from the NetBSD Project, where it appeared	first in NetBSD	1.4.  Support
     for NSS modules first appeared in FreeBSD 5.1.

     Luke Mewburn <> wrote this	freely-distributable name-ser-
     vice switch implementation, using ideas from the ULTRIX svc.conf(5) and
     Solaris nsswitch.conf(4) manual pages.  The FreeBSD Project added the
     support for threads and NSS modules, and normalized the uses of
     nsdispatch() within the standard C	library.

BSD				April 16, 2003				   BSD


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