link.php

<?php
function get_content_link( &$content, $remove = false ) {
  if ( empty( $content ) )
		return;

	$lines = explode( "\n", $content );
	$line = trim( array_shift( $lines ) );

	if ( 0 === stripos( $line, 'http' ) ) {
		if ( $remove )
			$content = trim( join( "\n", $lines ) );

		return esc_url_raw( $line );
	} else {
		if ( ! preg_match( '/<a\s[^>]*?href=[\'"](.+?)[\'"]/is', $content, $matches ) )
			return false;

		return esc_url_raw( $matches[1] );
	}
}

function get_the_link( $id = 0 ) {
	$post = empty( $id ) ? get_post() : get_post( $id );
	if ( empty( $post ) )
		return;

	if ( has_post_format( 'link', $post ) ) {
		$meta = get_post_format_meta( $post->ID );
		if ( ! empty( $meta['url'] ) )
			return esc_url_raw( $meta['url'] );
	}

	if ( ! empty( $post->post_content ) )
		return get_content_link( $post->post_content );
}

function the_link() {
	echo get_the_link();
}