The Unix Heritage Society mailing list
 help / Atom feed
From: Richard Tobin <richard@inf.ed.ac.uk>
To: "Erik E. Fair" <fair-tuhs@netbsd.org>,
	The Eunuchs Hysterical Society <tuhs@tuhs.org>
Subject: Re: [TUHS] Unix filesystem semantics history - files with holes
Date: Thu, 11 Apr 2019 16:57:48 +0100 (BST)
Message-ID: <20190411155748.8791B255ADDC@macaroni.inf.ed.ac.uk> (raw)

> When did the Unix filesystem add the semantics for "files with holes" (large,
> sparse files)?

It was there in the first edition:

https://www.bell-labs.com/usr/dmr/www/pdfs/man51.pdf

The FILE SYSTEM (V) man page includes a last paragraph identical to
that of FILSYS (V) in seventh edition:

  If block b in a file exists, it is not necessary that all blocks
  less than b exist.  A zero block number either in the address words
  of the the i-node or in an indirect block indicates that the
  corresponding block has never been allocated.  Such a missing block
  reads as if it contained all zero words.

The first edition indirect blocks were a bit different though: if the
file was bigger than 8 blocks (4kB), all the blocks in the inode were
(singly) indirect.

-- Richard

-- 
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.


         reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-11  2:37 Erik E. Fair
2019-04-11  5:28 ` Ronald Natalie
2019-04-11 15:57 Richard Tobin [this message]
2019-04-11 19:09 ` William Corcoran
2019-04-11 19:49 ` Bakul Shah

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190411155748.8791B255ADDC@macaroni.inf.ed.ac.uk \
    --to=richard@inf.ed.ac.uk \
    --cc=fair-tuhs@netbsd.org \
    --cc=tuhs@tuhs.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

The Unix Heritage Society mailing list

Archives are clonable: git clone --mirror http://inbox.vuxu.org/tuhs

Newsgroup available over NNTP:
	nntp://inbox.vuxu.org/vuxu.archive.tuhs


AGPL code for this site: git clone https://public-inbox.org/ public-inbox