Subject: Help with RT-11 'Split' Utility

From: Barry Skidmore <[email-masked]>
Date: Thu Jul 31 20:42:00 2003

I am having problems with the unsupported 'split' utility on a
PDP-11/23+ running RT-11 5.03

I am trying to split a 35000 block file into 3 files of similar sizes. 
I understand that you use octal values for block boundaries.  Here is
the command line that I have been using unsuccessfully:

The octal value of 35000 is 104270.

.split bak1.dsk,bak2.dsk,bak3.dsk=jul28.dsk/b:34757:69513
(where 69513 = 104270-34757)

However, I receive the following error:
?SPLIT-E-Invalid command

I need some help on how to specify the block boundaries.

Thanks,
Barry

-- 
Barry Skidmore <[email-masked]>

---

From: "Jerome H. Fine" <[email-masked]>
Date: Thu Jul 31 21:01:19 2003

>Barry Skidmore wrote:

> Barry Skidmore <[email-masked]>

Jerome Fine replies:

I looked at the arguments for SPLIT and you are correct, but
unfortunately, the octal arithmetic:
47311 = 104270 - 34757
seems to be the problem, aside from the fact that an octal value
can not include the digits 8 or 9.

When you posed this question on alt.sys.pdp11, I noticed
that you also received the error message:
?Split-E-Input error
This would probably be due to a bad block somewhere in
the last portion of the "JUL28.DSK" file.  Finding that block
will not be impossible, but when you do so, there are methods
to copy the bad block it can be recovered by repeated attempts
to read it ONE block at a time.  That attempt can sometimes
be accomplished by:

MOUNT  LD0:  JUL28.DSK/NOWRITE
COPY/DEVICE/IGNORE  LD0: DU1:

Finding the actual block that is bad is not trivial, but BINCOM
can help if you then do a binary search when comparing the
portions of LD0: which can be read.  If you don't understand,
please ask!

I presume that you have more than ONE  RT-11 partition to
work with although your sample syntax does not demonstrate
that possibility.  I presume that since every RT-11 partition
has a MAXIMUM of 65536 blocks and placing all 3 portions
of a 35000 block file on the same RT-11 partition would
require 70000 blocks - which exceeds that capacity of the
RT-11 partition.  Thus, even if you had not encountered
a bad block in the "JUL28.DSK" file, there would have been
insufficient space to output the last portion.

If you have any other RT-11 questions or require more
help, please ask.

Sincerely yours,

Jerome Fine
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