Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S271479AbTGQRc4 (ORCPT ); Thu, 17 Jul 2003 13:32:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S271503AbTGQRc4 (ORCPT ); Thu, 17 Jul 2003 13:32:56 -0400 Received: from [213.4.129.129] ([213.4.129.129]:1896 "EHLO tfsmtp2.mail.isp") by vger.kernel.org with ESMTP id S271479AbTGQRcb (ORCPT ); Thu, 17 Jul 2003 13:32:31 -0400 From: RAMON_GARCIA_F To: linux-kernel@vger.kernel.org Message-ID: Date: Thu, 17 Jul 2003 19:47:11 +0200 X-Mailer: Netscape Webmail MIME-Version: 1.0 Content-Language: es Subject: Suggestion for a new system call: convert file handle to a cookie for transfering file handles between processes. X-Accept-Language: es Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2172 Lines: 57 Hello. I suggest to add a new system call for transfering a file handle between two processes. In Linux, transfer of file handles can be done through a Unix domain socket. This mechanism is quite unflexible. It requires that the two applications connect by this kind of socket, and it is difficult to use from shell scripts. The new mechanims proposed is more flexible. A cookie is a large integer number (160 bit suggested) that can be used to refer to a file handle from any process. It is randomly choosen by the kernel at creation time. Afterwards, any process that knows this cookie can convert it back to a file handle. When this conversion is done, the cookie dies and is no longer valid. An example of why cookies are useful. Let cdwritter be a program for writting CDs. Unlike other programs, cdwritter is rationally designed. It is a server process that listens through a named pipe, thus making it easy to write either command line or graphical interfaces that use its functionality. The named pipe is called /var/run/cdwritter To keep this discussion simple, cdwritter supports writting a single file (usually an ISO image) to a cdrecorder. The user gives a command, and afterwards the CD is burned. To write a file, the user must write a string "write " to /var/run/cdwritter. The cookie is used to identify the file. An alternative would be that cdwritter accepts a file name instead of a cookie. But then, the author of cdwritter would have to check if the user has permission to access the file. This makes cdwritter more error prone. Shell scripts can write CDs to cdwriter. The command get_cookie, opens a file given on the command line and prints a cookie on stdout. Thus a shell script for burning the image my_nude_photos.iso would be: echo "write $(get_cookie my_nude_photos.iso)" > /var/run/cdwritter CREDITS: The Plan9 operating system provided inspiration for this idea. Ramon - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/