using dir() to get timestamp of file with ms precision

Hi there,

I am looking to extract the timestamp (specifically, the "modification date") of some files in a folder. If I use dir(), then I can get the modification date in either datetime or datenum format. However, both of these give the timestamp to second precision, but I know the actual timestamp has millisecond precision. I want that millisecond precision. Is there any way to get the timestamp with millisecond precision using dir()? If not, how can I do this?

Thanks in advance!

Answer 1

[supernoob]

As Walter Roberson mentioned, this is impossible with dir(). One could use Jan's solution though that was not appropriate in this case. I ended up using shell.

Answer 2

[Jan]

Under Windows you can use the C-Mex functions FEX: Filetime

[supernoob]

Thanks! It would be great to find a solution for Mac too, I work on both.

I would still like to find a Matlab-only solution :)

[Walter Roberson]

There is no MATLAB-only solution -- not unless you count making a Java call as a MATLAB solution.

[supernoob]

Hi Walter, that's good to know! It's looking like I may have to do this without Matlab.

[supernoob]

Jan,

I've been testing your script and it's nice, but there is a discrepancy between my system timestamps and the one your script generates. It looks like it is due to a rounding error. For example, looking directly at my system timestamp i see something like 2017-03-06 21:14:54.419710500 where your script returns 2017-03-06 12:14:54.418999999

It looks like this is some kind of rounding error.

Of course, I know that the timestamp can't be trusted much past microseconds anyways, but I'd like to do the rounding myself.

[supernoob]

follow up: I did this in shell then saved a csv to import into matlab

[Jan]

@supernoob: The function GetFileTime can reply the time in the native format as stored in the file system as UINT64 counted in steps of 100ns. Then you can convert this how ever you like it.

The C-Mex function uses the Windows library function FileTimeToSystemTime, which rounds to milliseconds.

[supernoob]

@Jan, thanks that's good to know. It seems likely the rounding error was from the FileTimeToSystemTime.