Adds a new row that shows the file size under an individual attachment dashboard page

wp3.5-attachments-filesize.php

<?php

/**
 * Adds a new row that shows the file size under an individual attachment dashboard page
 * 
 * @author Maor Chasen
 */
function mc_attachment_submitbox_filesize() {
	$post = get_post();
	$filesize = @filesize( get_attached_file( $post->ID ) );

	if ( ! empty( $filesize ) && is_numeric( $filesize ) && $filesize > 0 ) : ?>
		<div class="misc-pub-section">
			<?php _e( 'File size:' ); ?> <strong><?php echo size_format( $filesize ); ?></strong>
		</div>
	<?php
	endif;
}
add_action( 'attachment_submitbox_misc_actions', 'mc_attachment_submitbox_filesize' );