Restrict user to open same file instance

[vermarajeev]

Hi all,
How can I restrict a user to open the same file on multiple instances of the same application???? If you have word installed, then open multiple instances of it and try opening the same file on all the application...The user is restricted. How can I achieve this???

Thanks

[JosAH]

Hi all,
How can I restrict a user to open the same file on multiple instances of the same application???? If you have word installed, then open multiple instances of it and try opening the same file on all the application...The user is restricted. How can I achieve this???

Thanks

Word does it like this: if it wants to open a file "foo.doc" it tries to create a file
"~$foo.doc". If it doesn't exist word creates it, writes the name of the user in
that file and opens "foo.doc".

If that funny file already exists, word 'knows' that another word instance is
already editing that file and it also knows who is editing that file.

When an editing session is done, word simply removes that "~$foo.doc" file
again.

This scenario works because file creation is an atomic process on most (if not
all) file systems.

kind regards,

Jos

[vermarajeev]

Hi Jos,
Thanks for your reply.

I am working on an application where I can open multiple instances of same aplication. Presently the user is able to open the same file in any instances. The files are in text format. Can you provide me with some resources or something that can help me.

Waiting eagerly
Thanks

[AdrianH]

Word does it like this: if it wants to open a file "foo.doc" it tries to create a file
"~$foo.doc". If it doesn't exist word creates it, writes the name of the user in
that file and opens "foo.doc".

If that funny file already exists, word 'knows' that another word instance is
already editing that file and it also knows who is editing that file.

When an editing session is done, word simply removes that "~$foo.doc" file
again.

This scenario works because file creation is an atomic process on most (if not
all) file systems.

kind regards,

Jos

If you open a file with exclusive rights (read/write) wouldn't that stop you from opening it again in the same process as well as others?


Adrian

[JosAH]

If you open a file with exclusive rights (read/write) wouldn't that stop you from opening it again in the same process as well as others?


Adrian

It depends on the file system being used on a platform but I suspect what you
just descibed also works when one uses MS Windows. The OP wanted to know
how word does it however, so obediently I answered in my reply ;-)

kind regards,

Jos

[vermarajeev]

If you open a file with exclusive rights (read/write) wouldn't that stop you from opening it again in the same process as well as others?


Adrian

Any resources with some sample programs???? I think mandatory locks can be some point of initiation. Can you suggest some links or so...

Thanks

[AdrianH]

Any resources with some sample programs???? I think mandatory locks can be some point of initiation. Can you suggest some links or so...

Thanks

As Jos said, it depends on the file system/operating system. See CreateFile() in windows Win32 for info on that platform. www.microsoft.msdn.com should get you there where you can search the MSDN website.


Adrian