From: will.senn@gmail.com (Will Senn)
Subject: [TUHS] why does tar have the tape device hard coded into it and why is it mt1 instead of mt0
Date: Fri, 11 Dec 2015 16:27:28 -0600 [thread overview]
Message-ID: <566B4DD0.6070700@gmail.com> (raw)
All,
In my exploration of v6, I followed the advice in "Setting up Unix -
Seventh Edition" and copied v6tar from v7 to v6. Life is good. However,
tar is using mt1 and it is hard coded into the source, tar.c:
char magtape[] = "/dev/mt1";
As the subject line suggested, I have two questions for those of you who
might know:
1. Why is it hard coded?
2. Why is it the second device and not the first?
Interestingly, it took me a little while to figure out it was doing this
because I didn't actually move files between v6 and v7 until today.
Before this my tests had been limited to separate tests on v6 and v7
along the lines of:
cd /wherever
tar c .
followed by
tar t
list of files
cd /elsewhere
tar x
files extracted and matching
What it was doing was writing to the non-existant /dev/mt1, which it
then created, tarring up stuff, and exiting. Then when I listed the
contents of the tarfile, or extracted the contents, it was successful.
But, when I went to move the tape between v6 and v7, the tape (mt0) was
blank, of course. It was at this point that I followed Noel's advice
and "Used the source", and figured out that it was hard-coded as you see
above.
Thanks,
Will
next reply other threads:[~2015-12-11 22:27 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-11 22:27 Will Senn [this message]
2015-12-11 22:31 ` Clem Cole
2015-12-11 22:52 ` Will Senn
2015-12-11 23:13 ` John Cowan
2015-12-12 0:26 ` Random832
2015-12-12 2:09 Doug McIlroy
2015-12-12 18:54 ` Mary Ann Horton
2015-12-12 19:58 ` Armando Stettner
2015-12-12 20:13 ` Clem Cole
2015-12-12 22:44 ` Lyndon Nerenberg
2015-12-12 20:57 ` John Cowan
2015-12-12 17:17 [TUHS] TUHS] " Doug McIlroy
2015-12-12 20:17 ` [TUHS] " Diomidis Spinellis
2015-12-13 1:41 Norman Wilson
2015-12-13 3:04 ` Lyndon Nerenberg
Reply instructions:
You may reply publicly 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=566B4DD0.6070700@gmail.com \
--to=will.senn@gmail.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).