Reading the Event Log

The following example reads all the records in the Application log file and displays the event identifier, event type, and event source for each event log entry.

void DisplayEntries( )
{
    HANDLE h;
    EVENTLOGRECORD *pevlr; 
    BYTE bBuffer[BUFFER_SIZE]; 
    DWORD dwRead, dwNeeded, cRecords, dwThisRecord = 0; 
 
    // Open the Application event log. 
 
    h = OpenEventLog( NULL,             // use local computer 
             "Application");   // source name 
    if (h == NULL) 
        ErrorExit("Could not open the Application event log."); 
 
    pevlr = (EVENTLOGRECORD *) &bBuffer; 
 
    // Opening the event log positions the file pointer for this 
    // handle at the beginning of the log. Read the records 
    // sequentially until there are no more. 
 
    while (ReadEventLog(h,                // event log handle 
                EVENTLOG_FORWARDS_READ |  // reads forward 
                EVENTLOG_SEQUENTIAL_READ, // sequential read 
                0,            // ignored for sequential reads 
                pevlr,        // pointer to buffer 
                BUFFER_SIZE,  // size of buffer 
                &dwRead,      // number of bytes read 
                &dwNeeded))   // bytes in next record 
    {
        while (dwRead > 0) 
        { 
            // Print the event identifier, type, and source name. 
            // The source name is just past the end of the 
            // formal structure. 
 
            printf("%02d  Event ID: 0x%08X ", 
                dwThisRecord++, pevlr->EventID); 
            printf("EventType: %d Source: %s\n", 
                pevlr->EventType, (LPSTR) ((LPBYTE) pevlr + 
                sizeof(EVENTLOGRECORD))); 
 
            dwRead -= pevlr->Length; 
            pevlr = (EVENTLOGRECORD *) 
                ((LPBYTE) pevlr + pevlr->Length); 
        } 
 
        pevlr = (EVENTLOGRECORD *) &bBuffer; 
    } 
 
    CloseEventLog(h); 
}