Is file is being used

[Eran.Yasso]

Hi,

I have a mdb file shared in the LAN. I want to write app that verifies
if it's open.
If the file is not open, then my app can open the file.
if the file is used, then the app won't open it.

I also want this app to have handle to this file, then when the user
stops editting this file, he can close it using this app.

so my questions are:

1. How can i tell if a file is being used(edited, open, etc'...)
2. How can i close file(and save the data)?

TIA.

[Peter Duniho]

<Er********@gma il.comwrote in message
news:11******** **************@ j72g2000cwa.goo glegroups.com.. .

1. How can i tell if a file is being used(edited, open, etc'...)

Try to open it with exclusive access. If you succeed, it's not being used.

2. How can i close file(and save the data)?

Data is "saved" as you write to the file, though not necessarily the exact
moment you do so. You can use the Close method on the various file i/o
classes to ensure that the file is actually closed and the buffers have been
completely flushed.

Pete

[Rad [Visual C# MVP]]

On 12 Dec 2006 06:03:04 -0800, Er********@gmai l.com wrote:

Hi,

I have a mdb file shared in the LAN. I want to write app that verifies
if it's open.
If the file is not open, then my app can open the file.
if the file is used, then the app won't open it.

I also want this app to have handle to this file, then when the user
stops editting this file, he can close it using this app.

so my questions are:

1. How can i tell if a file is being used(edited, open, etc'...)
2. How can i close file(and save the data)?

TIA.

If I'm not wrong a MDB generates a temporary lock file when it is open,
with the same name but the extension .LDB. You can try checking for the
existence of that file to know if its is open

As for closing it from another application -- not sure about that
--
Bits.Bytes
http://bytes.thinkersroom.com

[Eran.Yasso]

Rad [Visual C# MVP] wrote:

On 12 Dec 2006 06:03:04 -0800, Er********@gmai l.com wrote:

Hi,

I have a mdb file shared in the LAN. I want to write app that verifies
if it's open.
If the file is not open, then my app can open the file.
if the file is used, then the app won't open it.

I also want this app to have handle to this file, then when the user
stops editting this file, he can close it using this app.

so my questions are:

1. How can i tell if a file is being used(edited, open, etc'...)
2. How can i close file(and save the data)?

TIA.

If I'm not wrong a MDB generates a temporary lock file when it is open,
with the same name but the extension .LDB. You can try checking for the
existence of that file to know if its is open

As for closing it from another application -- not sure about that
--
Bits.Bytes
http://bytes.thinkersroom.com

Oh man, thanks.
Now I know what's that ldb mean. Lock data base.
thanks, i wounder if i ldb file holds any information on the user who's
using the file and if i can parse the file.

does the ldb file is being deleted when the mdb file is stopped being
used?
does the ldb file is being created as soon as someone else opens the
file?

Maybe i should get response to this in WinAPI news group?

[Eran.Yasso]

Peter Duniho wrote:

<Er********@gma il.comwrote in message
news:11******** **************@ j72g2000cwa.goo glegroups.com.. .

1. How can i tell if a file is being used(edited, open, etc'...)

Try to open it with exclusive access. If you succeed, it's not being used.

2. How can i close file(and save the data)?

Data is "saved" as you write to the file, though not necessarily the exact
moment you do so. You can use the Close method on the various file i/o
classes to ensure that the file is actually closed and the buffers have been
completely flushed.

Pete

Hi Pete thanks for the response,
How can i use the exclusive access?
is it a class?

thanks,

[Rad [Visual C# MVP]]

On 12 Dec 2006 13:09:57 -0800, Er********@gmai l.com wrote:

Oh man, thanks.
Now I know what's that ldb mean. Lock data base.
thanks, i wounder if i ldb file holds any information on the user who's
using the file and if i can parse the file.

does the ldb file is being deleted when the mdb file is stopped being
used?
does the ldb file is being created as soon as someone else opens the
file?

Maybe i should get response to this in WinAPI news group?

Yep. It creates the lock as soon as the database is opened and deletes it
as soon as the database is closed.

Try it and see. Open the mdb in access and then navigate to the folder in
Windows Explorer
--
Bits.Bytes
http://bytes.thinkersroom.com

[Peter Duniho]

<Er********@gma il.comwrote in message
news:11******** **************@ j44g2000cwa.goo glegroups.com.. .

Hi Pete thanks for the response,
How can i use the exclusive access?
is it a class?

No...it's simply a part of the parameters you pass when you open the file.
I believe that the default is to open read/write with exclusive access, so
you may not have to specify anything at all. You should check the
documentation to be sure though.

[Peter Duniho]

"Rad [Visual C# MVP]" <no****@nospam. comwrote in message
news:kt******** ******@thinkers room.com...

Yep. It creates the lock as soon as the database is opened and deletes it
as soon as the database is closed.

Note that using the presence or content of the .ldb file isn't the right
answer for the original question.

Between the time one looks to see if the .ldb file exists, the status of the
database file could change. Knowing whether the .ldb file exists at time A
tells you nothing about whether you can successfully open the .mdb file at
time B.

If you want to know whether you can successfully open a file exclusively,
the only correct solution is to attempt to open the file exclusively. Any
other method can only provide hints as to whether the operation will succeed
or not, and in particular one will *always* still have to handle the case
where the operation fails even though there's no .ldb file at the time one
checks.

This is a classic issue for a wide variety of computer resources that one
desires to gain exclusive rights to. Whether a file, mutex, i/o port,
whatever...the only reliable means of determining whether one can get access
is to try getting access. Any other method wastes time checking something
that may or may not be valid later when one actually tries to get access.

Pete

[Rad [Visual C# MVP]]

On Tue, 12 Dec 2006 14:45:36 -0800, Peter Duniho wrote:

"Rad [Visual C# MVP]" <no****@nospam. comwrote in message
news:kt******** ******@thinkers room.com...

>Yep. It creates the lock as soon as the database is opened and deletes it
as soon as the database is closed.

Note that using the presence or content of the .ldb file isn't the right
answer for the original question.

I beg to differ.

He asked quite explicitly *How can i tell if a file is being used(edited,
open, etc'...)* What you're saying about exclusive use may be true, but is
not what OP asked.

The presence of the lock file is a perfectly valid answer to the question
of whether the file has been opened or not.
--
Bits.Bytes
http://bytes.thinkersroom.com

[Peter Duniho]

"Rad [Visual C# MVP]" <no****@nospam. comwrote in message
news:6o******** ******@thinkers room.com...

I beg to differ.

He asked quite explicitly *How can i tell if a file is being used(edited,
open, etc'...)* What you're saying about exclusive use may be true, but is
not what OP asked.

The presence of the lock file is a perfectly valid answer to the question
of whether the file has been opened or not.

Beg to differ all you want. His intent is clear to me. In addition to what
you quoted, he also wrote:

"If the file is not open, then my app can open the file."

and

"I also want this app to have handle to this file"

His application cannot open the file unless it's not already open by someone
else, and the only way to know whether he will be successful in opening the
file is to try doing it. Checking for the presence of a .ldb file tells him
nothing. If the file is absent, the .mdb file could still be unopenable,
and if the file is there, it's still possible that his application could
open the .mdb. The presence of the .ldb doesn't tell him anything about
whether he can actually open the .mdb file or not.

His post is clearly intended to not only find out whether the file has been
opened, but whether HIS application can open it. In any case, even if he
wants to know only whether the .mdb file is open, again...the only way to do
that is to look at that file. There is no way to atomically open one file
and create another simultaneously, and so there is no way a second file can
provide 100% accurate information about the state of another file.

Of course, neither of us will know for sure what his intent is unless he
posts and clarifies. But it's my opinion that his initial post is clear
enough, and he clearly wants access to the .mdb file. Even if he doesn't,
he can't reliably know the state of the .mdb file by looking at something
other than the .mdb file.

Pete