Manual Pages  — NSDISPATCH

retval is passed to each method to modify as necessary, to pass back results 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 arbitrary 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. Modules must use source names different from the built-in ones.

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;
        uint32_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 default rules.

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

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

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.