OpenEuphoria

RV: DOS undocumented feature

• Posted by rforno at tutopia.com Jul 22, 2002
• 360 views

I discovered that attributes (hidden, system, etc.) have nothing to do with
the ability to read a file. The only problem lies in that the culprit file
is locked by another program, that can be the same program. For example, if
you issue:
ex whatever > xx
then sometimes (not always, I don't know why), the whatever program cannot
read from xx.
Then, the problem reduces itself to this: how to know if a file is locked
before actually reading it, because if you attempt to read it, you get the
"Critical error" and have to key i (ignore).
----- Original Message -----
From: Ricardo M. Forno <rforno at tutopia.com>
To: <EUforum at topica.com>
Subject: RE: DOS undocumented feature


> Yes, it is a good idea.
> I have another one: store the attributes, set them to no-system,
no-hidden,
> read the files, and afterwards restore the original attributes. It is a
bit
> dangerous, however.
> Independently of attributes, in Windows there are some files that can't be
> accessed, for example the swap file. There are some others that are "in
use"
> by some other program, and can't be deleted, for example, without
restarting
> Windows. I found a way to treat some files that can't be deleted; they
*can*
> be moved to some other directory, and then you can delete them. Strange,
uh?
> ----- Original Message -----
> From: Kat <gertie at PELL.NET>
> To: EUforum <EUforum at topica.com>
> Sent: Sunday, July 21, 2002 5:11 PM
> Subject: Re: DOS undocumented feature
>
>
> >
> > On 21 Jul 2002, at 12:15, Robert Craig wrote:
> >
> > >
> > > Ricardo Forno writes:
> > > > While trying to enhance your DUPFILE.EXW program
> > > > with some additional options, I discovered what seems
> > > > to be an undocumented feature of DOS under
> > > > Windows 98 SE. This happens only in a DOS window,
> > > > not when you restart in DOS mode.
> > > > As you know, . means the current directory, and .. means the parent
> > > > directory. But ... means the parent of the parent directory,
> > > > .... the parent of the parent of the parent, and so on.
> > >
> > > That apparently doesn't work on XP. Only . and .. work.
> > >
> > > > So, maybe the number of possible platforms should be increased.
> > >
> > > I'm not sure what you mean. dupfile.exw works (more or less) on all
> > > platforms. Only "." and ".." are reported by the system calls that
dir()
> > > uses. I guess "..." and "...." are supported artificially by the
> > > Win 98 command-line processor.
> >
> > Which means you can write Eu code to artificially support it too,
Ricardo.
> > Same as adding a huge long path with create_directory().
> >
> > > > Do you know why some files processed by DUPFILE.EXW when run
> > > > through ex raise a "Critical error" condition?
> > >
> > > That's what DOS does when a DOS program tries to open a locked file.
> > > Not very helpful. It will help if you close all your Windows apps
> > > before scanning the whole drive with ex dupfile.exw.
> >
> > Even less helpful, Rob. What about checking the file attributes before
any
> > operations on them, Ricardo?
> >
> > Kat
> >
> >
> >
> >