using_mod_rewrite_permalinks example

// Ensure get_home_path() is declared.     require_once ABSPATH . 'wp-admin/includes/file.php';

    $home_path     = get_home_path();
    $htaccess_file = $home_path . '.htaccess';

    /* * If the file doesn't already exist check for write access to the directory * and whether we have some rules. Else check for write access to the file. */
    if ( ! file_exists( $htaccess_file ) && is_writable( $home_path ) && $wp_rewrite->using_mod_rewrite_permalinks()
        || is_writable( $htaccess_file )
    ) {
        if ( got_mod_rewrite() ) {
            $rules = explode( "\n", $wp_rewrite->mod_rewrite_rules() );

            return insert_with_markers( $htaccess_file, 'WordPress', $rules );
        }
    }

    return false;
}