check file opened or not?

Hello everyone,


On Windows platform, which API could be used to check whether a file is opened (either by other thread or process or even the same thread) or not?

C++ is fine.


thanks in advance,
George

You can try to open the file with "NO sharing", then it will fail if some other process has the file open.

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Mats

Thanks Mats,


You mean ::OpenFile() with OF_SHARE_EXCLUSIVE?

Quote:

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Originally Posted by matsp

You can try to open the file with "NO sharing", then it will fail if some other process has the file open.

--
Mats

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regards,
George

ifstream is fine.

Thanks Elysia,


You mean filebuf::sh_none?

Quote:

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Originally Posted by Elysia

ifstream is fine.

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regards,
George

ifstream::open with appropriate open protection constants, which I don't know what they're called or located.

when you say a file do you mean a process or what , because your making it sound like a .txt file

Quote:

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Originally Posted by Anddos

when you say a file do you mean a process or what , because your making it sound like a .txt file

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I think George2 is asking about files like .txt and such.

--
Mats

Thanks Elysia,


What do you mean "what they're called or located"?

Quote:

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Originally Posted by Elysia

which I don't know what they're called or located.

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Thanks Anddos,


I mean data files, like .txt or something. Any ideas to my original question?

Quote:

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Originally Posted by Anddos

when you say a file do you mean a process or what , because your making it sound like a .txt file

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regards,
George

Thanks Mats,


Right Mats!

Quote:

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Originally Posted by matsp

I think George2 is asking about files like .txt and such.

--
Mats

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regards,
George

Quote:

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Originally Posted by George2

Thanks Elysia,
What do you mean "what they're called or located"?

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I mean I don't know how to call ifstream with appropriate arguments.

Thanks Elysia,


So you mean you are not sure whether using filebuf::sh_none is correct?

Quote:

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Originally Posted by Elysia

I mean I don't know how to call ifstream with appropriate arguments.

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regards,
George

I don't know, but I doubt it. The class takes its arguments from ios_base.

and to check if its open ?
i would check if the process notepad is open then use FindWindow to check is the string of the windowtext is matching your textfile description

George wants to find out if the file is open, not if a process is open. And this doesn't just include Notepad. What you describe is a really horrible way of doing it.

no he said he wants to check if a file is open ,
by other thread or process or even the same thread
you need to learn to read dude!!!!!!!!!!!

And where does that say "notepad"?

notepad is a process you nubcake , if he wants to know if a txt file is open then this is the way !!!!!!!!
i will write the code out for you later on seeing as i am a nice guy

Notepad is one process. A file is a file and can be held open by one or more processes, not limited to notepad.
This is NOT the way.
Opening the file in exclusive mode is an easy way to know if another process is already holding the file open or not.

You need to learn to be less rude.

he said a txt file , so the default editor to open a .txt is notepad ,
the method you said means to open the file not check if the txt file is running !!! jesus christ

I will repeat the original message:

Quote:

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Originally Posted by George2

Hello everyone,

On Windows platform, which API could be used to check whether a file is opened (either by other thread or process or even the same thread) or not?

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In other words: how can I figure out if another process (or another thread) is holding the file open?
Answer: open in exclusive mode. This will fail unless the file is not opened by any other process.
If it succeeds, then the file is not open by any other process.

And even though notepad may be the default, it doesn't mean it's the only process that can hold a file open! George did mention "another thread," too, which could mean another thread in the same process perhaps? That's not notepad.

Anddos, chill out and stop attacking Elysia. There is no reason to inflame an otherwise calm thread.

Windows, AFAIK, has no command that will tell you which file handles belong to which threads. There are several undocumented NT_ functions within the kernel code that you can call but since they are undocumented and also subject to change I don't know if I would rely on these. I researched this one time to write a utility that would allow me to view which process had a file open and if need be attempt to gain ownership of that handle and close the file. This would eliminate the infamous 'Access denied. ..' error that really only helps viruses and spyware continue to run unmolested on your system.

There is a website that keeps a database of undocumented Win32 API functions that you can google for and that may assist you. I know it is possible to do this since there are utils out there that can tell you this information.

ifstream will only tell you about the process in which it is used. For system wide information about which file handles are being used and by whom you would have to make a call into the Windows kernel. There is no way the C/C++ standard libraries will know anything about other tasks or processes in the system that may have files open.

Thanks Bubba,


Two more comments,

1.

Do you mean there are some methods from ifstream class, which can tell which handle is used by which process? I have performed some research, but failed.

Could you indicate which method from ifstream do you mean from which we can know which process opens the file please? :-)

2.

Quote:

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Originally Posted by Bubba

Windows, AFAIK, has no command that will tell you which file handles belong to which threads. There are several undocumented NT_ functions within the kernel code that you can call but since they are undocumented and also subject to change I don't know if I would rely on these. I researched this one time to write a utility that would allow me to view which process had a file open and if need be attempt to gain ownership of that handle and close the file. This would eliminate the infamous 'Access denied. ..' error that really only helps viruses and spyware continue to run unmolested on your system.

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You mean there is public API in ifstream which can tell which process opens the file, not there is no open API to tell which thread opens the file?


Thanks Elysia,


You correctly understand my points. To be honest, my English is not very good, but you can understand all of my points. Appreciated. :-)

(Or, it means you have the same level of English skills -- just joking.)

Quote:

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Originally Posted by Elysia

I will repeat the original message:



In other words: how can I figure out if another process (or another thread) is holding the file open?
Answer: open in exclusive mode. This will fail unless the file is not opened by any other process.
If it succeeds, then the file is not open by any other process.

And even though notepad may be the default, it doesn't mean it's the only process that can hold a file open! George did mention "another thread," too, which could mean another thread in the same process perhaps? That's not notepad.

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regards,
George

Quote:

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Originally Posted by George2

Do you mean there are some methods from ifstream class, which can tell which handle is used by which process? I have performed some research, but failed.

Could you indicate which method from ifstream do you mean from which we can know which process opens the file please? :-)

You mean there is public API in ifstream which can tell which process opens the file, not there is no open API to tell which thread opens the file?

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No, that's not right. There is no method in ifstream to tell you that. There are undocumented Win32 API that does, however.

Have a look at http://undocumented.ntinternals.net/
Just beware of using these functions. They are usually undocumented for a reason.

Thanks Elysia,


Looks like Bubba is more familiar with ifstream class. :-)

Let me wait for him to see whether option filebuf::sh_none is the one for my question.

Quote:

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Originally Posted by Elysia

No, that's not right. There is no method in ifstream to tell you that. There are undocumented Win32 API that does, however.

Have a look at http://undocumented.ntinternals.net/
Just beware of using these functions. They are usually undocumented for a reason.

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regards,
George

Bubba explicitly told you that ifstream doesn't work:

Quote:

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Originally Posted by Bubba

Anddos, chill out and stop attacking Elysia. There is no reason to inflame an otherwise calm thread.

Windows, AFAIK, has no command that will tell you which file handles belong to which threads. There are several undocumented NT_ functions within the kernel code that you can call but since they are undocumented and also subject to change I don't know if I would rely on these. I researched this one time to write a utility that would allow me to view which process had a file open and if need be attempt to gain ownership of that handle and close the file. This would eliminate the infamous 'Access denied. ..' error that really only helps viruses and spyware continue to run unmolested on your system.

There is a website that keeps a database of undocumented Win32 API functions that you can google for and that may assist you. I know it is possible to do this since there are utils out there that can tell you this information.

ifstream will only tell you about the process in which it is used. For system wide information about which file handles are being used and by whom you would have to make a call into the Windows kernel. There is no way the C/C++ standard libraries will know anything about other tasks or processes in the system that may have files open.

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Hi Elysia,


To my requirement, I only need to know whether the file is opened by other process/thread or not, no need to know the exact process/thread ID.

So, I think filebuf::sh_none should be fine?

Quote:

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Originally Posted by Elysia

Bubba explicitly told you that ifstream doesn't work:

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regards,
George

An yes, found it. filebuf::sh_none will open the file in exclusive mode, so it should work to tell you if the file is open or not.

Thanks Elysia,


Question answered.

Quote:

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Originally Posted by Elysia

An yes, found it. filebuf::sh_none will open the file in exclusive mode, so it should work to tell you if the file is open or not.

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regards,
George

I don't think using ifstream is the right approach. Windows would be the only one who could really tell you if the file was opened by a process. Just because a file is opened in one process does not mean that it is in exclusive mode. This is actually relying on a side effect of what Windows may do to get ifstream to report the information you want. In essence you are using ifstream to report something that it is not responsible for.

Quote:

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Originally Posted by Bubba

I don't think using ifstream is the right approach. Windows would be the only one who could really tell you if the file was opened by a process. Just because a file is opened in one process does not mean that it is in exclusive mode. This is actually relying on a side effect of what Windows may do to get ifstream to report the information you want. In essence you are using ifstream to report something that it is not responsible for.

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I take it you mean that filebuf::sh_none is not guaranteed to open the file in "exclusive mode" - which is what is required for this to work.

--
Mats

Thanks Bubba,


What is your proposed solution if you do not propose to use ifstream below?

Quote:

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Originally Posted by Bubba

I don't think using ifstream is the right approach. Windows would be the only one who could really tell you if the file was opened by a process. Just because a file is opened in one process does not mean that it is in exclusive mode. This is actually relying on a side effect of what Windows may do to get ifstream to report the information you want. In essence you are using ifstream to report something that it is not responsible for.

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Hi Mats,

Quote:

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Originally Posted by matsp

I take it you mean that filebuf::sh_none is not guaranteed to open the file in "exclusive mode" - which is what is required for this to work.

--
Mats

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I think it is guaranteed. Here is what MSDN said,

http://msdn2.microsoft.com/en-us/lib...33(VS.60).aspx

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filebuf::sh_none Exclusive mode — no sharing.
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Any comments?


regards,
George