stevesu@bronze.UUCP (Steve Summit) (11/11/83)
I have a couple of questions about with Eunice that somebody out
there may be able to answer.
Why are files with 512 byte fixed length records the default for
creat()? To get a variable-length record, carriage-control file
(which is what I usually want, for a text file) you have to add
the optional third "txt" argument to the creat() call.
Apparently the editors have been rewritten in this way, but (at
least in our version) sh and tar have not. Files created with >
output redirection, and those created by tar, always end up with
512 byte fixed-length records. The vms utilities like type and
print can't deal with these files, and they don't work as shell
scripts or vms command files either. Is there a good reason why
512 byte fixed records is the default?
The other day I had occasion to archive a bunch of files
(actually, my whole directory) using tar, and then restore them.
I had been doing (vms) purge/keep=2 all the time, so I had two
versions of most files. Suppose I had versions ;4 and ;5.
Version ;5 wrote to the tape without a version number, and
version ;4 wrote to the tape with a .4 tacked on. When they read
back in, the one without a version number (which had been ;5) got
created with version number ;1, but version ;4 stayed ;4.
Suddenly all of my older files had higher version numbers!
This unfortunate behavior makes perfect sense given Eunice's
version number mapping algorithm. (A second problem was that all
the files were 512 byte fixed-length records again, and had to be
fixed up using an editor, thus destroying the correct last-
modified date.) Has anyone figured out a way to make large
backup/restore's work correctly?
Steve Summit
tektronix!tekmdp!stevesu