[TUHS] v6tar from v7 on v6, too large?

Noel Chiappa jnc at mercury.lcs.mit.edu
Sat Dec 19 23:27:52 AEST 2015

So, speaking of system calls that are missing in earlier versions of Unix,
that tickled a memory:

    > From: Will Senn

    > ... a special version of tar must be prepared to run on V6.
    > The document goes on to describe a reasonable method to make v6tar on
    > v7 and copy the binary over to the v6 system.

When I got tar running on my V6, I didn't know about this, and I took
a V7 tar and got it running myself, see here:

One thing I found out while doing that is that tar uses the 'utime' system
call on V7 to set the file date, but i) V6 doesn't have utime() (although it
has smdate(), albeit commented out in the standard distro), and ii) on now
looking in src/cmd/tar and src/libc/v6 in the V7 distro, I don't see a
replacement version of utime().

As near as I can make out, 'v6tar' must be using the standard V7 version of
utime(), which I assume turns into a call to nosys() on V6 (returns an error);
tar doesn't check the return value, so the call fails (silently). So v6tar
won't correctly set the file date when moving a file _to_ V6.


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