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Re: Reliable old script loses data on new Cygwin installation


On Mon, Nov 12, 2007 at 04:03:14AM -0600, René Berber wrote:
> [snip]
> > However, the other problem (see below) has occurred --
> > sporadically -- on three different machines, all running
> > German or English-language versions of XP, two with SATA
> > disks and one with an ATA disk, all with freshly downloaded
> > installations of cygwin.[snip]
> 
> OK, that's interesting, 3 machines one using non SATA disk.  Same
> irregular pattern of 10 to 20 runs without problem?

I haven't run it enough to see clear patterns, but yes,
the error occurs in an irregular manner.  Since then I have
tested this on a fourth machine -- my old machine, with newly
installed XP and freshly downloaded Cywin but a slower hard
disk -- and I get the same irregular errors there too!

> No.  The actual storage of data is done by the operating system, not by
> Cygwin, the operating system provides the data even if it hasn't been
> stored on disk (it could still be in a memory buffer).

Okay, thank you for the explanation.

> The speed is not the problem, it could be the usual suspect: an
> anti-virus, unlikely because the data written is not executable but it
> could be adding an extraneous delay between data written and data read.

I'll ask the guy who installed the operating systems whether this
looks possible.

> The only solid evidence is the error message from Windows, and it says
> "device", that means that the hard disk is having problems (it could be
> the driver) but not your script or any program.  Did you do anything
> special to the hard disks on all 3 machines? something like run an
> optimizer or tune parameters?

I'll find out.

> The other problem could be related to the first, if the disk is
> "failing" then creating/moving a file will fail, I'm not sure if
> "permission denied" will be the error message but I could test that
> later (I can make my SATA disk fail using a program that allows the
> async unbuffered I/O).

The /bin/pdksh script sequence that is causing problems is:

   1. gawk '$1 !~ /blahblah/' huh2 >|/tmp/shf2080.tmp
      (no error messages)

   2. mv /tmp/shf2080.tmp huh2
      mv: cannot create regular file `huh2': Permission denied

   3. (some other commands in a looping construct)

   4. gawk '$1 !~ /blahblah/' huh2 >|/tmp/shf2080.tmp
      gawk: cmd. line:1: fatal: cannot open file `huh2' for reading (No such file or directory)

Sometimes the sequence runs correct.  Sometimes it results in a
file "huh2" with length "0".  But the sequence has _sometimes_
resulted in the creation of files such as:

   - 2007-10-28  20:31       4010  german

which _appear_ to have a length of 4010, but where "od german"
shows:

    0000000 000000 000000 000000 000000 000000 000000 000000 000000
    *
    0007640 000000 000000 000000 000000 000000
    0007652

I'll get answers to the questions above...

Tom Baker

-- 
Tom Baker - tbaker@tbaker.de - baker@sub.uni-goettingen.de

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