How to get drupal 7 default file upload directory?
This information is saved in Drupal's variables table. Use the variable_get function to get this information, passing in the name of the correct variable:


Public Filesystem Location: variable_get('file_public_path', conf_path() . '/files');
Private Filesystem Location: variable_get('file_private_path');


If you want the temporary upload directory use variable_get('file_temporary_path'); If you want to determine the system specific upload directory, regardless of the actual site configuration use the file_directory_temp function.

variable_get('file_public_path', conf_path() . '/files'); will pull the default path for you in case it has not been modified or explicitly set by the site administrator.