Open your functions.php file and paste the following function in it:
function show_file_func( $atts ) {
extract( shortcode_atts( array(
'file' => ''
), $atts ) );
if ($file!='')
return @file_get_contents($file);
}
add_shortcode( 'show_file', 'show_file_func' );
Once done, you can use the shortcode. It’s pretty simple:
[show_file file="http://www.test.com/test.html"]
Thanks to Vladimir Prelovac for the handy tip!