I'm unfamiliar with static classes and from my reading believe I have it setup correctly although I get a long list of undefined references. If anyone could advise me the correct approach or what I am doing wrong would really appreciate it!

header file:

```
 #ifndef _SYSTEMLOGGING_h
 #define _SYSTEMLOGGING_h
 #define BUF_LENGTH 45

 #if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
 #else
#include "WProgram.h"
 #endif
 #include "EepromStorage.h"

 class SystemLogging
 {
 public:
    static bool writeLog(char logName[5], char timeStamp[9], char itemId[3], char deviceName[11], char value[6], char duration[5], char state[3] );

  private:
    static char logBuff[BUF_LENGTH];
    static char logname[9];
    static uint32_t length;
    static int lineCount;
    static int data;
 };

 #endif

```

c++ file

```
 #include <SdFat.h>
 #include <SdFatUtil.h>
 #include "SystemLogging.h"

 extern SdFile g_file;
 extern SdFile g_root;

 bool SystemLogging::writeLog(char logName[5], char timeStamp[9], char itemId[3], char deviceName[11], char value[6], char duration[5], char state[3] ){
    memset(SystemLogging::logBuff, 0, BUF_LENGTH);
    strncpy (SystemLogging::logname, "XXXX.LOG", 9);
    strncpy (SystemLogging::logname, logName, 4);
    if (!g_file.open(&g_root,SystemLogging::logname, O_RDWR | O_CREAT )) { //create if dosent exist
        PgmPrintln("Log Write Error");
        return false;
    } else {
        SystemLogging::length = g_file.fileSize();
        g_file.setpos(0);
        SystemLogging::lineCount = 0;
        SystemLogging::data = 0;
        while((data = g_file.read()) > 0)
        {
            if(data == '\n')
                SystemLogging::lineCount++;
        }
        if(lineCount>99)
            g_file.setpos(0);
        strcpy(SystemLogging::logBuff,timeStamp + ':');
        strcat(SystemLogging::logBuff,itemId + ':');
        strcat(SystemLogging::logBuff,deviceName + ':');
        strcat(SystemLogging::logBuff,value + ':');
        strcat(SystemLogging::logBuff,duration + ':');
        strcat(SystemLogging::logBuff,state + '\n');
        g_file.print(SystemLogging::logBuff);
        g_file.close();
    }
    return false;
 }  

```

Compiler error:

```
 Compiling 'asas' for 'Arduino Mega 2560 or Mega ADK'
 SystemLogging.cpp.o : : In function `SystemLogging::writeLog(char*, char*, char*, char*, char*, char*, char*)':
 SystemLogging.cpp : logBuff'
 SystemLogging.cpp : logBuff'
 SystemLogging.cpp : logname'
 SystemLogging.cpp : logname'
 SystemLogging.cpp : logname'
 SystemLogging.cpp : logname'
 SystemLogging.cpp : logname'
 SystemLogging.cpp.o : :C:\Users\Tim\AppData\Local\VMicro\Arduino\Builds\asas\mega2560\SystemLogging.cpp:16: more undefined references to `SystemLogging::logname' follow
 SystemLogging.cpp.o : : In function `SystemLogging::writeLog(char*, char*, char*, char*, char*, char*, char*)':
 SystemLogging.cpp : length'
 SystemLogging.cpp : length'
 SystemLogging.cpp : length'
 SystemLogging.cpp : length'
 SystemLogging.cpp : lineCount'
 SystemLogging.cpp : lineCount'
 SystemLogging.cpp : data'
 SystemLogging.cpp : data'
 SystemLogging.cpp : lineCount'
 SystemLogging.cpp : lineCount'
 SystemLogging.cpp : lineCount'
 SystemLogging.cpp : lineCount'
 SystemLogging.cpp : data'
 SystemLogging.cpp : data'
 SystemLogging.cpp : lineCount'
 SystemLogging.cpp : lineCount'
 SystemLogging.cpp : logBuff'
 SystemLogging.cpp : logBuff'
 SystemLogging.cpp : logBuff'
 SystemLogging.cpp : logBuff'
 SystemLogging.cpp : logBuff'
 SystemLogging.cpp.o : :C:\Users\Tim\AppData\Local\VMicro\Arduino\Builds\asas\mega2560\SystemLogging.cpp:33: more undefined references to `SystemLogging::logBuff' follow
 Error creating .elf

```

Thanks for your help!