C语言截取字符串

void subString(char filePath)
{
       int len = strlen(filePath);
       int num, n;
       char buf[128] = {0};
       char cutOff[128] = {0}; 
     
       strcpy(buf, filePath);
       for(num = len - 1; num > 0; num--){
             if(buf[num] == "\")
             {
                   n = num;
                   for(num = n+1; num < len; num++){
                         cutOff[num-n-1] = buf[num];
                   }    
                   break; 
             }  
      }       
}