描述：

更新附件(图片/文件)的路径

用法：

<?php update_attached_file( $attachment_id, $file ) ?>

参数：

$attachment_id

(integer) (必填) Attachment ID

默认值: None

$file

(string) (必填) File path for the attachment

默认值: None

源文件：

/**
 * Update attachment file path based on attachment ID.
 *
 * Used to update the file path of the attachment, which uses post meta name
 * '_wp_attached_file' to store the path of the attachment.
 *
 * @since 2.1.0
 *
 * @param int    $attachment_id Attachment ID.
 * @param string $file          File path for the attachment.
 * @return bool True on success, false on failure.
 */
function update_attached_file( $attachment_id, $file ) {
	if ( !get_post( $attachment_id ) )
		return false;

	/**
	 * Filter the path to the attached file to update.
	 *
	 * @since 2.1.0
	 *
	 * @param string $file          Path to the attached file to update.
	 * @param int    $attachment_id Attachment ID.
	 */
	$file = apply_filters( 'update_attached_file', $file, $attachment_id );

	if ( $file = _wp_relative_upload_path( $file ) )
		return update_post_meta( $attachment_id, '_wp_attached_file', $file );
	else
		return delete_post_meta( $attachment_id, '_wp_attached_file' );
}