Review the Plug-In

The following example logs Hello, World! at Directory Server startup.

Example 4–1 Hello, World! Plug-In (hello.c)

#include "slapi-plugin.h"

Slapi_PluginDesc desc = { 
    "Hello, World",                    /* plug-in identifier      */
    "Sun Microsystems, Inc.",          /* vendor name             */
    "6.0",                             /* plug-in revision number */
    "My first plug-in"                 /* plug-in description     */
};

/* Log a greeting at server startup if info logging is on for plug-ins */
int
hello()
{
    slapi_log_info_ex(
        SLAPI_LOG_INFO_AREA_PLUGIN,    /* Log if info logging is  */
        SLAPI_LOG_INFO_LEVEL_DEFAULT,  /* set for plug-ins.       */
        SLAPI_LOG_NO_MSGID,            /* No client at startup    */
        SLAPI_LOG_NO_CONNID,           /* No conn.  at startup    */
        SLAPI_LOG_NO_OPID,             /* No op.    at startup    */
        "hello() in My first plug-in", /* Origin of this message  */
        "Hello, World!\n"              /* Informational message   */
    );
    return 0;
}

/* Register the plug-in with the server */
#ifdef _WIN32
__declspec(dllexport)
#endif
int
hello_init(Slapi_PBlock * pb)
{
    int rc = 0;                        /* 0 means success         */
    rc |= slapi_pblock_set(            /* Plug-in API version     */
        pb,
        SLAPI_PLUGIN_VERSION,
        SLAPI_PLUGIN_CURRENT_VERSION
    );
    rc |= slapi_pblock_set(            /* Plug-in description     */
        pb,
        SLAPI_PLUGIN_DESCRIPTION,
        (void *) &desc;
    );
    rc |= slapi_pblock_set(            /* Startup function        */
        pb,
        SLAPI_PLUGIN_START_FN,
        (void *) hello
    );
    return rc;
}

To log the greeting, the plug-in includes a function to be called at Directory Server startup. The plug-in also includes an initialization function to register the plug-in description, supported API version, and startup function with Directory Server.

The startup function specifies that the message is from a plug-in, SLAPI_LOG_INFO_AREA_PLUGIN. The startup function also specifies that the message should be logged when informational logging is activated, SLAPI_LOG_INFO_LEVEL_DEFAULT. For this log message, no client connection information is available, SLAPI_LOG_NO_MSGID, SLAPI_LOG_NO_CONNID, SLAPI_LOG_NO_OPID. Directory Server calls the function at startup before any clients have connected. The function specifies where the log message originates, "hello() in My first plug-in". Finally, the function provides the famous log message.

The initialization function is named hello_init(). This function modifies the parameter block, pb, with the function slapi_pblock_set(). The function thus registers the plug-in API version supported, the plug-in description, and the functions offered to Directory Server by this plug-in. As required for all plug-in initialization functions, hello_init() returns 0 on success, -1 on failure. The function slapi_pblock_set() returns 0 if successful, -1 otherwise. Therefore, you do not need to set the return code to -1 explicitly in Example 4–1.