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40 .Nd name-service switch dispatcher routine
50 .Fa "const ns_dtab dtab[]"
51 .Fa "const char *database"
52 .Fa "const char *method_name"
53 .Fa "const ns_src defaults[]"
59 function invokes the methods specified in
65 until a successful entry is found.
68 is passed to each method to modify as necessary, to pass back results to
72 Each method has the function signature described by the typedef:
75 .Fn \*(lp*nss_method\*(rp "void *retval" "void *mdata" "va_list *ap" ;
80 structures, which have the following format:
81 .Bd -literal -offset indent
82 typedef struct _ns_dtab {
91 array should consist of one entry for each source type that is
94 as the name of the source,
96 as a function which handles that source, and
98 as a handle on arbitrary data to be passed to the method.
109 Additionally, methods may be implemented in NSS modules, in
110 which case they are selected using the
114 arguments along with the configured source.
115 Modules must use source names different from the built-in ones.
118 contains a list of default sources to try if
120 is missing or corrupted, or if there is no relevant entry for
124 structures, which have the following format:
125 .Bd -literal -offset indent
126 typedef struct _ns_src {
134 array should consist of one entry for each source to be configured by
139 set to the criterion desired
143 .Sx Method return values
144 for more information).
155 For convenience, a global variable defined as:
157 .Dl extern const ns_src __nsdefaultsrc[];
159 exists which contains a single default entry for the source
161 that may be used by callers which do not require complicated default
165 are optional extra arguments, which are passed to the appropriate method
166 as a variable argument list of the type
168 .Ss Valid source types
169 While there is support for arbitrary sources, the following
170 #defines for commonly implemented sources are available:
171 .Bl -column NSSRC_COMPAT compat -offset indent
172 .It Sy "#define value"
173 .It Dv NSSRC_FILES Ta \&"files\&"
174 .It Dv NSSRC_DB Ta \&"db\&"
175 .It Dv NSSRC_DNS Ta \&"dns\&"
176 .It Dv NSSRC_NIS Ta \&"nis\&"
177 .It Dv NSSRC_COMPAT Ta \&"compat\&"
182 for a complete description of what each source type is.
183 .Ss Method return values
186 functions must return one of the following values depending upon status
188 .Bl -column "Return value" "Status code"
189 .It Sy "Return value Status code"
190 .It Dv NS_SUCCESS Ta success
191 .It Dv NS_NOTFOUND Ta notfound
192 .It Dv NS_UNAVAIL Ta unavail
193 .It Dv NS_TRYAGAIN Ta tryagain
194 .It Dv NS_RETURN Ta -none-
199 for a complete description of each status code.
203 function returns the value of the method that caused the dispatcher to
210 provides stubs for compatibility with NSS modules
216 However, these stubs only support the use of the
224 .Xr nsswitch.conf 5 ,
229 function first appeared in
231 It was imported from the
234 where it appeared first in
236 Support for NSS modules first appeared in
239 .An Luke Mewburn Aq Mt lukem@netbsd.org
240 wrote this freely-distributable name-service switch implementation,
251 added the support for threads and NSS modules, and normalized the uses
254 within the standard C library.