On Tue, 13 Jul 1999, Luigi Rizzo wrote: > > > Hi, i have a question. > > > > > > Why 'dd' does not seek over 'char' devs (specifically raw disk > > > partitions). > > > > Not all character devices support seeking. So, we work with the LCD... > > Sorry, I don't like this either. It would be better, maybe, just to fix > > character devices. > > couldn't we first try lseek and only do the reads on char devs where > the lseek fails ?
lseek() won't usually fail unless it's something like EBADF. It merely sets the current fd's offset. It would be nice to be able to tell from a device driver if it supports seeking (da) or not (sa). Hmm... actually, if we just specify somehow that we support either direct or sequential access... this would be possible. > > > You certainly make a good case. modify your local copy of dd to do > > what you want. > > generally this is not the kind of things you can do when your system > has already gone bad (this was a laptop's disk...) > The problem is that dd skip= is used a lot on tape devices. Here, a seek would not work. > > > > > > I notice that on output lseek _is_ used also on char devices. > > > > And how else would you do it? > > ok, stupid observation! > > cheers > luigi > > -----------------------------------+------------------------------------- > Luigi RIZZO, lu...@iet.unipi.it . Dip. di Ing. dell'Informazione > http://www.iet.unipi.it/~luigi/ . Universita` di Pisa > TEL/FAX: +39-050-568.533/522 . via Diotisalvi 2, 56126 PISA (Italy) > > http://www.iet.unipi.it/~luigi/ngc99/ > ==== First International Workshop on Networked Group Communication ==== > -----------------------------------+------------------------------------- > > > To Unsubscribe: send mail to majord...@freebsd.org > with "unsubscribe freebsd-hackers" in the body of the message > Brian Fundakowski Feldman _ __ ___ ____ ___ ___ ___ gr...@freebsd.org _ __ ___ | _ ) __| \ FreeBSD: The Power to Serve! _ __ | _ \._ \ |) | http://www.FreeBSD.org/ _ |___/___/___/ To Unsubscribe: send mail to majord...@freebsd.org with "unsubscribe freebsd-hackers" in the body of the message
