Source

File: wp-includes/general-template.php

function get_search_query( $escaped = true ) {
	/**
	 * Filters the contents of the search query variable.
	 *
	 * @since 2.3.0
	 *
	 * @param mixed $search Contents of the search query variable.
	 */
	$query = apply_filters( 'get_search_query', get_query_var( 's' ) );

	if ( $escaped ) {
		$query = esc_attr( $query );
	}
	return $query;
}