Source

File: wp-includes/general-template.php

function the_search_query() {
	/**
	 * Filters the contents of the search query variable for display.
	 *
	 * @since 2.3.0
	 *
	 * @param mixed $search Contents of the search query variable.
	 */
	echo esc_attr( apply_filters( 'the_search_query', get_search_query( false ) ) );
}