From mboxrd@z Thu Jan 1 00:00:00 1970 From: dave@horsfall.org (Dave Horsfall) Date: Tue, 21 Nov 2017 10:22:28 +1100 (EST) Subject: [TUHS] Determining what was on a tape back in the day In-Reply-To: <1511201558.524826.1178671936.79EC560B@webmail.messagingengine.com> References: <20171119134109.59F3018C0F5@mercury.lcs.mit.edu> <7AA20D14-571A-4AAD-96D0-45057F5B81DD@jctaylor.com> <1CE2C7FC-1FAE-44F7-8DDA-B21D54FA0E43@ronnatalie.com> <1511201558.524826.1178671936.79EC560B@webmail.messagingengine.com> Message-ID: On Mon, 20 Nov 2017, Random832 wrote: > For whatever it's worth, the tm(4) and ht(4) manpages from V5 onward say > "seeks have their usual meaning", and both drivers provide a 'non-raw' > device which is a block device and (according to the manual) only > supports tapes consisting of 512-byte records - the BUGS section > mentions that the raw device, conversely, does *not* support seeking. Thank you; I dimly recall that seeks were implemented by the driver keeping track of whichever block was under the head, and skipping forwards or backwards accordingly, with simple arithmetic. I no longer have access to those sources, but we at UNSW certainly modified Unix rather heavily, so if that capability is not in the distributed version then it means that we modified it; this was over 30 years ago... It bloody well worked as a read-only file system; I take great umbrage at the implication that I am a liar, and I'm the sort of obstreperous bastard who neither forgives not forgets... -- Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."