WordPress at a glance
filter is not described

post_link filter-hook . WP 1.5.0

Filters the permalink for a post.

Only applies to posts with post_type of 'post'.

Usage

add_filter( 'post_link', 'filter_function_name_6152', 10, 3 );
function filter_function_name_6152( $permalink, $post, $leavename ){
	// filter...

	return $permalink;
}
$permalink(string)
The post's permalink.
$post(WP_Post)
The post in question.
$leavename(true/false)
Whether to keep the post name.

Where the hook is called

get_permalink()
wp-includes/link-template.php 240
return apply_filters( 'post_link', $permalink, $post, $leavename );

Where the hook is used (in WP core)

Does not used.