Re: emacs's dired display of Window's file permission

[Eli Zaretskii <eliz@gnu.org>]

> From: Xah Lee <xahlee@gmail.com>
> Newsgroups: gnu.emacs.help
> Date: Sun, 21 Jun 2009 14:31:21 -0700 (PDT)
> 
> On Windows, how's emacs's dired display map the Window's file
> permission?

If by "Windows file permissions" you mean the native NTFS file
security access rights, then Emacs on Windows currently doesn't look
at them at all.  What Emacs shows you is the effect of a single mode
bit: the read-only bit.  A file with the readonly bit set will be show
with only read access, otherwise both read and write will be shown.
The execute bit is _computed_ for executable programs and batch files.

In addition, the single rwx group computed as I explain above is
copied to the other 2 Posix groups, so, for example, a read-only
non-executable file will be shown as "r--r--r--".

> for example, emacs display this:
> 
>  -rw-rw-rw-  1 xah    None   814669 06-05 00:09 Snapshot_001.png

In light of the above, I believe you will understand why.

> however, cygwin termninal displays this:
> 
>  -rwx------+  1 xah    None   814669 Jun  5 00:09 Snapshot_001.png
> 
> The file's Properties shown in Explorer, has 3 group or users:
> 
>  SYSTEM
>  xah
>  Administrators

Cygwin uses NT security features to emulate Posix owner/group/world
standard access rights.  Emacs still doesn't.  We hope to add to Emacs
support for Windows ACLs in a future release.  But even then, Emacs
will not necessarily be compatible with Cygwin, because Posix
emulation is not the most important goal of the native Windows port of
Emacs.  In particular, Cygwin may do strange things with files whose
ACL is not set by a Cygwin program, while the native Windows port of
Emacs should work with these files as any other native Windows program
does.

If you want compatibility with Cygwin programs, use the Cygwin build
of Emacs.