How to create file with 0 bytes (length) ?
Dennis Halver
Dennis
Benjamin David Lunt
"Dennis Halver" <ha...@persrec.com> wrote in message
news:4a526f74$0$32682$9b4e...@newsspool2.arcor-online.net...
> How can I create a file with 0 byte length?
>
> Dennis
Using what? Since this is a MSDOS group, though I noticed
that you are coming from a NT Batch group, you can create
a zero length file many ways.
It has been a while, but if you uses DOS's Create_File
service call, then write zero bytes (CX = 0) to it,
then close is, won't that create a zero byte file?
IIRC, you *have* to call the Write_File service call
or DOS won't create the file entry. Just calling
the Create_File/Close_File service calls won't do it.
However, it have been a while so I may be wrong.
Ben
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pe...@nospam.demon.co.uk
> "Dennis Halver" <ha...@persrec.com> wrote in message
> news:4a526f74$0$32682$9b4e...@newsspool2.arcor-online.net...
> > How can I create a file with 0 byte length?
> >
> > Dennis
>
> Using what? Since this is a MSDOS group, though I noticed
> that you are coming from a NT Batch group, you can create
> a zero length file many ways.
>
> It has been a while, but if you uses DOS's Create_File
> service call, then write zero bytes (CX = 0) to it,
> then close is, won't that create a zero byte file?
>
> IIRC, you *have* to call the Write_File service call
> or DOS won't create the file entry. Just calling
> the Create_File/Close_File service calls won't do it.
>
> However, it have been a while so I may be wrong.
>
> Ben
I think it's not necessary, Ben -- at least it isn't here in
MSDOS 6.22. Maybe what you are recalling is the way to truncate
an existing file to zero bytes? In that case, you just seek to
the point in the file you want to make EOF (or in this case, the
beginning) and write zero bytes.
That said, I spent a few minutes playing around at the DOS prompt
and all that seems necessary is to run some command that writes
nothing to STDOUT and redirect to a file. For example:
echo. > tempfile.$$$
del tempfile.$$$ > zerosize.fil
creates a zero length file.
Dennis, why do you want a zero length file? Would a directory
entry suffice? Or even a volume label if you only need one such
and don't mind it being in the root dir.
Pete
--
"We have not inherited the earth from our ancestors,
we have borrowed it from our descendants."
Ted Davis
They are used as flags in batch files. There are a few other, rarely
encountered, uses as well. Mostly they are used by batch files to indicate
that some process (usually the batch file itself) is running and
additional instances should self abort. They are also used to signal when
a file is in use - sort of like a write lock - to prevent or allow other
batch files to use the file or wait until it's free.
--
T.E.D. (tda...@mst.edu)
ras...@highfiber.com
> That said, I spent a few minutes playing around at the DOS prompt
> and all that seems necessary is to run some command that writes
> nothing to STDOUT and redirect to a file. For example:
>
> echo. > tempfile.$$$
> del tempfile.$$$ > zerosize.fil
>
> creates a zero length file.
rem > tempfile.$$$
is one easy way; REM doesn't display anything to stdout. Even easier,
using 4DOS, is
> tempfile.$$$
i.e. redirect output without executing any command!
--
Charles Dye
Ted Davis
> rem > tempfile.$$$
That doesn't work in XP. I've never seen anyone actually use it, though
it might work in Real DOS.
A few years ago, I experimented with all the usual methods and found that
only one works in all the MS OSs:
type nul > file
--
T.E.D. (tda...@mst.edu)
ras...@highfiber.com
> On Tue, 07 Jul 2009 11:24:24 -0700, raster wrote:
> > rem > tempfile.$$$
>
> That doesn't work in XP. I've never seen anyone actually use it, though
> it might work in Real DOS.
It does. (I'm reading this in an MS-DOS group....)
> A few years ago, I experimented with all the usual methods and found that
> only one works in all the MS OSs:
>
> type nul > file
Very nice. That also works in 4DOS, Take Command, and the DR-DOS /
OpenDOS implementation of COMMAND.COM. I suppose the NUL device must
always return EOF on read.
--
Charles Dye ras...@highfiber.com
Jaelani
> On Jul 7, 6:09 pm, Ted Davis <tda...@mst.edu> wrote:
>> On Tue, 07 Jul 2009 11:24:24 -0700, raster wrote:
>>> rem > tempfile.$$$
>> That doesn't work in XP. I've never seen anyone actually use it, though
>> it might work in Real DOS.
>
> It does. (I'm reading this in an MS-DOS group....)
Odd... I should work.
But mine (XP SP3 CMD.EXE & COMMAND.COM) also don't work.
goto nowhere > file
works though.
ras...@highfiber.com
XP SP3 isn't MS-DOS.
--
Charles Dye
Zaphod Beeblebrox
"T Lavedas" <tglb...@cox.net> wrote in message
news:1cf74c95-922f-45b6...@t21g2000yqi.googlegroups.com...
>
> It appears the OP multi-posted and this same topic is covered in
> great
> detail over in alt.msdos.batch.nt,
>
Actually, he (yet again) crossposted and silently set followups to
AMBNT, and somewhere along the line the followup group got broken /
ignoted so that (yet again) the conversation got fragmented among the
various groups.
OP, if you are out there and reading this message, please do us the
courtesy of allowing the multipost to do what it was intended to do,
or at the very least indicate in the original post that you've set
followups to a specific group.
--
Zaphod
No matter where you go, there you are!
Ted Davis
> I suppose the NUL device must
> always return EOF on read.
It does ... more or less.
--
T.E.D. (tda...@mst.edu)
Ted Davis
> XP SP3 isn't MS-DOS.
True, but the original message had Followup-to: set to alt.msdos.batch.nt.
--
T.E.D. (tda...@mst.edu)
Richard Bonner
> ras...@highfiber.com wrote:
> > On Jul 7, 6:09 pm, Ted Davis <tda...@mst.edu> wrote:
> >> On Tue, 07 Jul 2009 11:24:24 -0700, raster wrote:
> >>> rem > tempfile.$$$
> >> That doesn't work in XP. I've never seen anyone actually use it, though
> >> it might work in Real DOS.
> >
> > It does.
> Odd... It should work.
> But mine (XP SP3 CMD.EXE & COMMAND.COM) also don't work.
> goto nowhere > file
> works though.
*** In DR-DOS, so does:
GOTO > FILE
A syntax error message appears, but the zero-byte file is created.
Richard Bonner
http://www.chebucto.ca/~ak621/DOS/