• For clean log, shell script already exist in path-to-magento/shell directory:

  php log.php Usage: php -f log.php -- [options] php -f log.php -- clean --days 1

  clean Clean Logs --days Save log, days. (Minimum 1 day, if defined - ignoring system value) status Display statistics per log tables help This help

For clean cache, following methods will help you to make a shell script:

• For clean log, shell script already exist in path-to-magento/shell directory:

  php log.php 
   Usage:  php -f log.php -- [options]
           php -f log.php -- clean --days 1
  
     clean             Clean Logs
     --days      Save log, days. (Minimum 1 day, if defined - ignoring system value)
     status            Display statistics per log tables
     help              This help

   

• For clean cache, following methods will help you to make a shell script:

  
   // Clean js and css
   Mage::getModel('core/design_package')->cleanMergedJsCss();
   Mage::dispatchEvent('clean_media_cache_after');
  
   // product image
   Mage::getModel('catalog/product_image')->clearCache();
   Mage::dispatchEvent('clean_catalog_images_cache_after');
  
   // Get cache types
   Mage::app()->getCacheInstance()->getTypes()
  
   // Clean specific tags
   Mage::app()->cleanCache($tags);
  
   // dispatch event if you flush all cache tags
   Mage::app()->cleanCache($alltags);
   Mage::dispatchEvent('adminhtml_cache_flush_system');