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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 {
88 .Bd -ragged -offset indent
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.
110 Additionally, methods may be implemented in NSS modules, in
111 which case they are selected using the
115 arguments along with the configured source.
116 (The methods supplied via
118 take priority over those implemented in NSS modules in the event
122 contains a list of default sources to try if
124 is missing or corrupted, or if there is no relevant entry for
128 structures, which have the following format:
129 .Bd -literal -offset indent
130 typedef struct _ns_src {
135 .Bd -ragged -offset indent
138 array should consist of one entry for each source to be configured by
143 set to the criterion desired
147 .Sx Method return values
148 for more information).
159 For convenience, a global variable defined as:
160 .Dl extern const ns_src __nsdefaultsrc[];
161 exists which contains a single default entry for the source
163 that may be used by callers which do not require complicated default
168 are optional extra arguments, which are passed to the appropriate method
169 as a variable argument list of the type
171 .Ss Valid source types
172 While there is support for arbitrary sources, the following
173 #defines for commonly implemented sources are available:
174 .Bl -column NSSRC_COMPAT compat -offset indent
175 .It Sy "#define value"
176 .It Dv NSSRC_FILES Ta """files""
177 .It Dv NSSRC_DNS Ta """dns""
178 .It Dv NSSRC_NIS Ta """nis""
179 .It Dv NSSRC_COMPAT Ta """compat""
184 for a complete description of what each source type is.
185 .Ss Method return values
188 functions must return one of the following values depending upon status
190 .Bl -column "Return value" "Status code"
191 .It Sy "Return value Status code"
192 .It Dv NS_SUCCESS Ta success
193 .It Dv NS_NOTFOUND Ta notfound
194 .It Dv NS_UNAVAIL Ta unavail
195 .It Dv NS_TRYAGAIN Ta tryagain
196 .It Dv NS_RETURN Ta -none-
201 for a complete description of each status code.
205 function returns the value of the method that caused the dispatcher to
212 provides stubs for compatibility with NSS modules
218 However, these stubs only support the use of the
226 .Xr nsswitch.conf 5 ,
231 function first appeared in
233 It was imported from the
236 where it appeared first in
241 wrote this freely-distributable name-service switch implementation,
252 added the support for threads and NSS modules, and normalized the uses
255 within the standard C library.