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by j4_james 2926 days ago
Interestingly, when you create a file name from the WSL shell using reserved Windows characters, those characters will get mapped to unicode codepoints from the private use area when viewed in Windows. So for example a colon (\u003A) will show up in Windows as \uF03A.

This means you can create a filename in Windows using the character \uF03A, and that character will show up in the WSL shell as a colon. You can even do the same thing with "regular" characters, e.g. using \uF061 instead of "a", and produce a filename that appears to be ASCII in the WSL shell, but is not actually accessible.
3 comments
lloeki 2926 days ago
Mac OS X maps filenames between slash `/` and colon `:` to match with UFS, the colon used to be the path separator on old MacOS, which HFS+ inherited.

Try it:

    $ touch foo:bar
    $ open .
    # Look at the filename in Finder.
    # Try it the other way around by saving a file
    # with / in TextEdit, then ls in Terminal.
[0]: https://stackoverflow.com/questions/13298434/colon-appears-a...
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chungy 2926 days ago
This is compatible with the mechanism Cygwin came up with: https://cygwin.com/cygwin-ug-net/using-specialnames.html#pat...
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cryptonector 2925 days ago
Oh dear. How fun!

These little sins are truly terrible.

I prefer openat(2) and friends for dealing with ADS. It means you have to have specialized programs to deal with them from shell scripts, as open(2) and friends provide no naming conventions for getting at ADS. This approach is much much safer than the WIN32 approach of using :$HACK_ME_PLEASE and :$THANK_YOU_MAY_I_HAVE_ANOTHER.

Note that Linux has openat(2), but it doesn't support ADS. Solaris/Illumos does. Linux has xattrs, which, like ADS in Solaris/Illumos, requires separate system calls to access -- no open(2) naming conventions there.

Both, ADS and xattrs are extremely useful. Let's say you need to associate some metadata with a file, but you can't change its contents' format. You could use some separate file that goes with it, but now you can't atomically rename(2) the thing... But with ADS/xattrs you just attach those to the file, and then when you rename(2) the file the ADS/xattrs go with it atomically. (Yes, you could rename a directory, but it doesn't quite have the same semantics as renaming a file. In particular, rename(2) of a directory won't rm -rf the target if it exists.)

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