What plugin for the_content_limit ?

Hi there, first post here, great community around, here is my first post in this forum:

I have seen a couple of issues with “the_content_limit” function, I also have the “fatal error: Call to undefined function the_content_limit()” message, I installed different plugins to make it work but no success up to now, can anybody help me ?
Here is my entire code for a sidebar in which I want to display 80 first words of 3 last posts of category 7. (only the_content_line function does not work).

<div id=”sidebar”>
<h2>Last Posts</h2>
<?php
$lastposts = get_posts(‘category=7&numberposts=3’);
foreach($lastposts as $post) :
setup_postdata($post);
?>
<h2>” id=”post-<?php the_ID(); ?>”><?php the_title(); ?></h2>
<?php the_content_limit(80, “read more ?”); ?>
<?php endforeach; ?>
</div>

Anybody can help me? Thanks!!