Proposal: Add Temporary and Sparse and to FileOptions

[msedi]

Discussed in #65067

^{Originally posted by msedi February 9, 2022}
From the WinAPI (https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea) I can see that there is a FILE_ATTRIBUTE_TEMPORARY flag when creating a file which seems to be very useful in my case.

The question in general is, does FILE_ATTRIBUTE_TEMPORARY have an effect? I assume some other flags its only a hint to the file manager. I can also understand that this is not available on other platforms, but if it can be seen as a hint only (windows), it could also be seen as such in other platforms.

Additionally the sparsity of a file could tremendously help to improve performance for large files. Currently there are two possibilities SetFileValidData or DeviceIoControl that allow to create sparse files.

Another solution might be

try
{                    
  File.SetAttributes(fileName, File.GetAttributes(fileName) | FileAttributes.Temporary);
}
catch
{
}

but this looks a bit clumsy.

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Issue Details

---

Discussed in #65067

^{Originally posted by msedi February 9, 2022}
From the WinAPI (https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea) I can see that there is a FILE_ATTRIBUTE_TEMPORARY flag when creating a file which seems to be very useful in my case.

The question in general is, does FILE_ATTRIBUTE_TEMPORARY have an effect? I assume some other flags its only a hint to the file manager. I can also understand that this is not available on other platforms, but if it can be seen as a hint only (windows), it could also be seen as such in other platforms. Additoinally the sparsity of a file could tremendously help to improve performance for large files. Currently there are two possibilities SetFileValidData or DeviceIoControl that allow to create sparse files.

Another solution might be

try
{                    
  File.SetAttributes(fileName, File.GetAttributes(fileName) | FileAttributes.Temporary);
}
catch
{
}

but this looks a bit clumsy.

Author:	msedi
Assignees:	-
Labels:	area-System.IO, untriaged
Milestone:	-

[danmoseley]

@msedi we have a particular format for API proposals like this one. Could you please update your top post to match the API proposal format, per this template
https://github.com/dotnet/runtime/issues/new?assignees=&labels=api-suggestion&template=02_api_proposal.yml&title=%5BAPI+Proposal%5D%3A+

Or simply close this and use that template to open a new one.

[adamsitnik]

@msedi it would be great if you could also provide some more information about why you need these features: example scenario that is impossible to implement as of today and some benchmark numbers for spare files

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[adamsitnik]

FWIW I did a quick check and Linux defines O_TMPFILE : https://man7.org/linux/man-pages/man2/open.2.html

macOS does not: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/open.2.html

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