From: utzoo!decvax!duke!unc!smb Newsgroups: net.unix-wizards Title: Re: mag tape ballots counted Article-I.D.: unc.3730 Posted: Sun Jul 25 21:33:58 1982 Received: Wed Jul 28 06:09:49 1982 Dare I suggest that UNIX follow the OS/360 model? Well, let me cite Multics instead -- it's a bit nicer, and there UNIX's debt is clear. Most of the time, I want to treat a file on a tape as a *file*. I rarely care about where on the tape it's located -- I want to find it, and read it, as many times as necessary to do what needs to be done. For example, I rarely extract a tar image without looking at the contents first; I *never* do if I'm running as root (and when will someone write some mods to tar that will let it rename files...?). When you mount a tape in OS/360 or Multics, you specify a file number. The operating system finds the file; when you close the tape drive, it repositions the tape to the start of that same file. You can read it over and over again if you'd like. (Both Multics and OS allow "labelled tapes"; Multics permits you to specify the file-name on the tape instead of the sequence number, while OS requires that they match.) There should be ioctl() calls to change the standard file number; calls like "write tape mark" should automatically increment it. Tape motion calls should of course exist -- but they should co-exist with this basic principle. Thus, 'backspace record' should halt at the tape mark -- you can't seek past the beginning of a file. But 'rewind' should reset the file number to 1. (Amdahl's UTS system has some of this implemented, though not the file-number concept. One nice thing they do do is generate a signal when a write encounters the end-of- volume mark -- the same signal they use to indicate that you've just filled up a file-system, duckie.)