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Aug 20th, 2005

how to set file access time

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Here the code where I'm trying to set last-accessed attribute of the file to some value.

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hFile = CreateFile(szDestName.GetBuffer(255), GENERIC_WRITE | GENERIC_READ, FILE_SHARE_WRITE | FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, 0);
 
GetFileTime(hFile,&createTime,&accessTime,&writeTime);
writeTime.dwHighDateTime -= 1000L;
accessTime = writeTime;
 
SetFileTime(hFile,&createTime,&accessTime,&writeTime);
// at this point access and write(modified) times are equal
CloseHandle(hFile);
// at this point access time is changed to the current system time
hFile = CreateFile(szDestName.GetBuffer(255), GENERIC_WRITE | GENERIC_READ, FILE_SHARE_WRITE | FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, 0);

GetFileTime(hFile,&createTime,&accessTime,&writeTime);
writeTime.dwHighDateTime -= 1000L;
accessTime = writeTime;

SetFileTime(hFile,&createTime,&accessTime,&writeTime);
// at this point access and write(modified) times are equal
CloseHandle(hFile);
// at this point access time is changed to the current system time

I suppose I didn't set the correct attributes in CreateFile function.
Does anybody knows how to do this correctly?

Last edited by Dave Sinkula; Aug 20th, 2005 at 3:40 pm. Reason: Added [code][/code] tags.

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akoloff

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Aug 20th, 2005

Re: how to set file access time

you can't control the time because, as you found out, the os will change it when the file is closed.

Quote originally posted by MSDN ...

Not all file systems can record creation and last access time and not all file systems
record them in the same manner. For example, on Windows NT FAT, create time has a
resolution of 10 milliseconds, write time has a resolution of 2 seconds, and access time
has a resolution of 1 day (really, the access date). On NTFS, access time has a
resolution of 1 hour. Therefore, the GetFileTime function may not return the same file
time information set using SetFileTime. Furthermore, FAT records times on disk in local
time. However, NTFS records times on disk in UTC, so it is not affected by changes in
time zone or daylight saving time.

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Aug 21st, 2005

Re: how to set file access time

I found out that if you use:

CreateFile(szDestName.GetBuffer(255), 0, FILE_SHARE_WRITE | FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, 0);

instead of:
CreateFile(szDestName.GetBuffer(255), GENERIC_READ | GENERIC_WRITE, FILE_SHARE_WRITE | FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, 0);

then you can't read or write to the file obviously BUT:
you can check for the file existence without changing
it's access time, which was good enough in my case.

Thanks for your reply anyway.

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Aug 21st, 2005

Re: how to set file access time

If all you wanted to do what check for the file's existance then use GetFileAttributes(). That function returns -1 if the file doesn't exist. Or you could also use _stat() function, which also returns error when file not found.

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