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Date: Thu, 14 Jul 2016 19:22:34 +0200
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: cygpath -w 'a"b'
Message-ID: <20160714172234.GB19533@calimero.vinschen.de>
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References: <000b01d1dddd$174e66a0$45eb33e0$@gmail.com> <C32E46D2-3984-427D-B6B6-50BF252FC8A1@etr-usa.com> <D6AABF23-1C86-4037-B862-57BCFFD5BC3C@etr-usa.com>
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On Jul 14 11:12, Warren Young wrote:
> On Jul 14, 2016, at 9:24 AM, Warren Young <wyml@etr-usa.com> wrote:
> >=20
> > If you look at such a file name in Explorer, Cygwin (?) seems to be map=
ping double-quotes to U+F022, which is currently not defined within Unicode:
> >=20
> >  http://www.fileformat.info/info/unicode/char/f022/
>=20
> I think this may be a typo in whatever code is doing the translation,
> because U+FF02 is a typographically distinct variation of the
> double-quote character:
>=20
>   http://www.fileformat.info/info/unicode/char/ff02/index.htm
>=20
> That would give the visual appearance of double-quotes in file names
> in Explorer without violating the restriction on 0x22 characters in
> NTFS.
>=20
> In fact, it might be a thinko rather than a typo: 0x22 -> 0xF022.  It
> looks like someone thought they could just add 0xF000 to the character
> value, when the correct value os 0xFF02.

Nope.  The idea(*) was *not* to provide a typiographically similar
character, the idea was to allow to express characters disallowed in the
Windows namespace but allowed in the POSIX namespace by transposing them
into the private use area on creating the filename and converting it
back to the untransposed ASCII char when reading the filename from disk.
You can't perform this action by converting the character to another
*valid* character.

Btw., there's a section in the Cygwin User's Guide on special characters:

https://cygwin.com/cygwin-ug-net/using-specialnames.html#pathnames-specialc=
hars


Corinna


(*) Original idea by the Interix folks, picked up by Cygwin for
    compatibility.

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