X-VM-v5-Data: ([nil nil nil nil nil nil nil t nil]
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Date:         Sat, 7 Jul 90 16:58:09 CET
Reply-To: LaTeX-L Mailing list <LATEX-L@DHDURZ1.uucp>
From: bbeeton <BNB@MATH.AMS.COM>
Subject:      Re: Permanence of .aux files
To: Rainer Schoepf <BK4@DHDURZ1.uucp>
Status: R
X-Status: 
X-Keywords:                  
X-UID: 170

don wants an example of a latex run where one really wants to keep
a previous version of an aux file.  this is easy!
picture a document with several parts (let's say 4), where it's
necessary to rerun part 2.  (the editor changed her mind.)  each part
starts on a new page, is in a separate file, and they are combined by
means of a "driver" file that inputs them one after another in the
right order.  parts 1, 3 and 4 have already been sent to the typesetter,
and there's enough slack in part 2 that the page numbers aren't going
to change.
all cross-references have been made symbolically, and citations use
labels rather than page numbers.  there are entries in the aux file
>from all 4 parts, and the citations cross part boundaries.  no new
references are being added, and none are being deleted.
the correction to part 2 consists of adding a section that is within
an environment, which should be wrapped in \begin{...} ... \end{...}.
but the correction is done in a hurry, and the \end{...} is forgotten
(or the ... is misspelled).  no way to recover this one!  poof goes the
good aux file!
now, it's true that in this case one would be insane not to keep a
backup copy of the good aux file under another name (the 3 parts that
have already been committed to film aren't going to be rerun for the
purpose of getting new camera copy under any circumstances).  even if
the correction went smoothly, though, the full aux file is gone, and
if you were in too much of a hurry to remember to keep the backup, ...
well, i don't usually keep .dvi files (the system managers are always
after me to free up space on the disks).  do you?  and after the camera
copy has been shipped to the printer, the boss asks you to send a copy
to the chairman of the board of trustees, and you find that the backup
photocopy is missing pages 11-16, do you really want to have to rerun
the whole thing twice?  (once is bad enough.)
this may seem preposterous, but it's real life in a production shop.
even the vms plea is false.  our system keeps only 3 versions of any
file, and at midnight, like cinderella's carriage, all but the latest
goes poof.  if the key work was done after the backups were run but
before the purge, then it's goodbye forever.
if this seems paranoid, and i've missed some easy way (other than the
obvious ones of manually keeping a backup, and not making mistakes in
the correction) of recovering from this mess, i'd love to hear them.
motto -- murphy always wins.
                                                -- bb
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