Copyfile with long path names

Question

Christoph 2013-5-22

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评论： Martin 2024-4-24

There seems to exist a limitation for the length of the file path when using the copyfile-command (something like 260 characters), because I get an 'Unknown error' when I want to copy to a destination with a longer path.

This seems to be related to a problem with the Windows copy+paste command (because I cannot even manually copy the files to that location). I googled the problem and it seems that there exist some workarounds for manual copy+paste. Do you know of any workarounds for this problem in Matlab?

My system: Windows 7 64-bit Matlab R2013a

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John 2024-4-23

Yes, I have. Just Google it and you will find everything. It is easy btw.

Martin 2024-4-24

I just installed the tool. I will soon share the reviews.

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Answer 1

Jan 2013-5-22

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编辑：Jan 2013-5-22

It is not a problem of Copy&Paste, but file names have this general limitation under Windows. E.g. the Windows Explorer cannot move files to the recycle bin, if their name is longer.

As workaround you can use the Windows API function and mask the name with the leading magic string '\\?\'. But a lot of important functions (like the already mentioned recycling) will not work. Even e.g. DIR fails for too long path and/or folder names (at least here the masking works, see also FEX: GetFullPath). Therefore I suggest three strategies:

Write an enhancement request to Microsoft. This is such a dull and idiotic limitation, which blocks a serious using of the system since the first DOS implementations. Try to reach Bill Gates personally, because he is responsible.
Use a serious operating system for serious tasks. Linux, Unix, Aix, BeOS, HP-UX, MacOS (7,8,9,X), Minix, BSD, Solaris, VMS, and even the Sinclair ZX Spectrum (1982) had no such limits in the file name length.
Use shorter file names, when you insist on using Windows for considerable reasons.

Note that very long file names usually mean, that the user inserts important information into the name, instead of storing it in the contents. But it is not efficient to store important information in the filesystem's name tables. A slightly exaggerated example: You can even store pictures in the name tables by using spaces and X as black&white pixels and using a very small font size for the command window, where the LS command is called. But then you cannot blame the OS, if you cannot use duplicate pixel rows or if the output is dosplayed in alphabetical order.

PS. Sometimes I think of inserting smilies in my messages, but I still hope my English is distinct enough to let the readers understand the intention without such extra markers. Of course I know, that Bill will no answer, but I'm impressed every time TMWs technical support responses to such enhancement requests.

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jack reacher 2017-12-15

use robocopy

Walter Roberson 2017-12-15

robocopy appears to refer to https://technet.microsoft.com/en-us/library/cc733145(v=ws.11).aspx

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Answer 2

Friedrich 2013-5-22

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编辑：Friedrich 2013-5-22

在 MATLAB Online 中打开

Hi,

have you tried to prefix \\?\ for the file path like mentioned here:

http://msdn.microsoft.com/en-us/library/aa365247%28VS.85%29.aspx

AFAIK MATLAB calls into the WIndows API function when using copyfile. At least my MATLAB doesnt complain when I build up a file path like

a = '\\?\C:\myfolder\test.dat'
copfyile(a,'C:\demo.dat')

And it also works. Does this work for you?

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Jan 2013-5-24

编辑：Jan 2013-5-24

在 MATLAB Online 中打开

The magic (another word for ugly here) string '\\?\' helps also, for scanning folders with long pathes by the DIR command. Unfortunately it is not the 260 characters limit, but some characters less. The length of the file names might matter also, but it cannot be known before getting the list. After some user requests, I've expanded GetFullPath, such that it can handle this securely:

List = dir(GetFullPath(Folder, 'fat'));

KAE 2018-1-8

在 MATLAB Online 中打开

In case it helps someone else, here is an example for the move command if you need to move a file with a long name to a subdirectory resulting in an even longer name so that the final filename would exceed the 260 character limit. There are double quotes to deal with spaces in the file or directory name.

eval(['!move "\\?\' longFilename '" "' subdirectoryMakingLongerFilename '"']);

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Answer 3

Iain 2013-5-24

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I'm not sure how you can reasonably use this or if it still exists in Win7.

There is a "short" name for every file and folder, which is restricted to 8 characters.

C:\docume~1\ is the short path for C:\documents and settings\.

It gets extremely hard to use if you have huge numbers of similarly named files, because the "~1" part gets longer and more complicated.

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Jan 2013-5-24

Fortunately the Windows API offers method to get the short name automatically, such that a simple Mex-File can achieve the conversion. But even the short name must fail, when the path of a file is deeply nested and even the resulting short name exceeds MAX_PATH characters. In addition error messages containing the abbrev. filename will look such ugly.

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