How do truncate and show read more, need help…

Heya, I feel like this is a really basic question and that I’m overlooking documentation but I can’t find anything on the topic. I’m writing a search.php page and I need to limit the text to a certain number of characters and show a “…” then a read more link. Can anyone help me out? Thanks!

<?php if (have_posts()) : ?>

		<h1>Search Results</h1>

		<div class="search-form"><?php get_search_form(); ?></div>

		<div class="navigation">
			<div class="alignleft">next<?php next_posts_link('&laquo; Older Entries') ?></div>
			<div class="alignright">previ<?php previous_posts_link('Newer Entries &raquo;') ?></div>
		</div>

		<?php while (have_posts()) : the_post(); ?>

			<a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a>

			<?php echo substr($post->post_content, 0, 200); ?>

			<hr />

		<?php endwhile; ?>

		<div class="navigation">
			<div class="alignleft"><?php next_posts_link('&laquo; Older Entries') ?></div>
			<div class="alignright"><?php previous_posts_link('Newer Entries &raquo;') ?></div>
		</div>

	<?php else : ?>

		<h2 class="center">No posts found. Try a different search?</h2>
		<?php get_search_form(); ?>

	<?php endif; ?>