Overriding MAX_PATH

MAX_PATH is the 260 character limit Windows places on file paths. Apparently the NTFS file path limit is 32,767 characters, and since Windows uses that file system, I'm not sure what the massive restriction is for. Whenever I transfer files between hard drives of different file systems, this bloody MAX_PATH variable seems to happily get in the way, if only by a few characters. And to make matters worse, although Windows tells you about the names of the several hundred or so files that didn't quite make the transfer due to their paths being over 260 characters, it doesn't have the courtesy to tell you where exactly those files are.

Since I expect I will continue transferring files in the near future, I have started taking a look at what is out there to override MAX_PATH. So far I have heard of Robocopy and I shall have a more in-depth look at it soon. I expect that there are also other solutions out there and that people here have attempted them, so before I commit too much to one solution that might not necessarily be the best one, it would be great to hear of any viable alternatives. Ideally there would be something that could be done "in-house", i.e. without having to rely on third-party software, to override MAX_PATH, but I'm not expecting miracles.

Also, if anyone knows of any way to obtain a record of the paths of any files that encountered errors during transfers and thereby possibly didn't get transferred, your input on this would also be appreciated.

Thank you for any help.

logicearth said:

Just use Robocopy as it was designed for what you want. Its built into Windows 7 so its not third-party well in terms of Windows. Furthermore, the 255 limit is an NTFS limit. I don't know where you got 32,767 but that is not it.

That's what I thought, but some people on Wikipedia seem to think otherwise. Best not to use an encyclopedia run by the public, as they say.

It's great that Robocopy is built in. I'll try it out after my current transfer is finished.

MAX_PATH isn't a parameter you can modify with some obscure registry technique, but rather is a constant defined in the Win32API C header files. The value comes from a limitation in the Windows API itself, as many file-handling functions take this value as the maximum allowable path length, so further folders would be truncated and programs react by preventing generating them in the first place. While the NTFS filesystem does allow longer paths, Windows itself cannot handle them correctly sometimes (I guess for compatibility reasons).

The NTFS file system has a maximum path limit of 32767 bytes. But you can only realize that if the software you are using doesn't impose a lower limit. As it turns out, many system functions and software do impose a lower limit of MAX_PATH. Changing this value is so close to impossible as to not matter.

At this point in time Microsoft can't change the value of MAX_PATH. Doing so would break an enormous amount of existing software.

You have 2 choices:
1. Use file copying software, such as Robocopy, that does not have the MAX_PATH limit. This will allow you to copy files with a long path but that won't help with software that recognizes this limit.
2. Keep path lengths within the limit.

robocopy works, but I wish there were some way to bypass max_path from startup using built-in drag-and-drop instead of having to start a program in admin mode and double-check precise commands. It might be fine for the occasional backup but when every other move is affected it starts getting annoying.