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#-----------------------------------------------------------------#
# Add file URL column to Media Library Admin
#-----------------------------------------------------------------#
function muc_column( $cols ) {
     $cols["media_url"] = "URL";
    return $cols;
}

function muc_value( $column_name, $id ) {
        if ( $column_name == "media_url" ) echo '<input type="text" width="100%" onclick="jQuery(this).select();" value="'. wp_get_attachment_url( $id ). '" readonly="true" />';
	}
	
add_filter( 'manage_media_columns', 'muc_column' );
add_action( 'manage_media_custom_column', 'muc_value', 10, 2 );
	
add_filter( 'manage_media_columns', 'sk_media_columns_filesize' );