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<?php

/**
 * WordPress shortcode allows you to create content that is visible only in your RSS feeds.
 *
 * Example: [feedonly]Dear RSS readers...[/feedonly]
 */
function feedonly_shortcode( $atts, $content = null) {
    if (!is_feed()) return "";
    return $content;
}
add_shortcode('feedonly', 'feedonly_shortcode');