apply_filters to content NOT FROM single, or page to execute shortcodes

Hi, i’m using shortcodes in my wordpress, shortcodes does alot of stuff for me -it enters data to database and so on, and i DO NOT DISPLAY content, i only need to run shortcodes, so : HOW to apply_filters from external php file, not from single.php or page.php? I tried to get post ID then by using query get post’s content and then apply filters to execute shortcodes – it’s not working.

i did like this:

function apdirbam_irasa($id){
	if (!empty($id)){
	global $wpdb,$post;
	$rez = $wpdb->get_row($wpdb->prepare("SELECT post_content FROM _posts WHERE id='%d'", $id), ARRAY_A);
	$turinys = $rez["post_content"];
	apply_filters('the_content', $turinys);
}
}

The reason why it’s not working-because of shorcode uses $id = $post->ID; to get post id and then by it runs shorcode, cause i’m calling it not from the loop so it doesn’t know the ID so it’s not working…how can i simulate apply_filters to run from post loop but not in single or page.php