Forcing Custom Permalinks in WordPress

Question

Programmatically, without me overwriting the .htaccess file, what's the trick to tell WordPress to switch on custom permalinks (like %postname%) so that it creates the special .htaccess file that gives us pretty URLs? I need this for a special theme I'm coding.

EDIT: Note, this isn't a sysop or end user question. It's a question directed at WordPress programmers. Read the question below from @anubhava below and you'll see my answer.

Answer 1

You can change the permalink structure via your functions.php theme file by doing the following

function change_permalinks() {
    global $wp_rewrite;
    $wp_rewrite->set_permalink_structure('/%category%/%postname%/');
    $wp_rewrite->flush_rules();
}
add_action('init', 'change_permalinks');