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Re: sed 4.2.1-1 locks files on windows
- From: Corinna Vinschen <corinna-cygwin at cygwin dot com>
- To: cygwin at cygwin dot com
- Date: Tue, 21 Feb 2012 12:45:00 +0100
- Subject: Re: sed 4.2.1-1 locks files on windows
- References: <email@example.com>
- Reply-to: cygwin at cygwin dot com
On Feb 21 11:58, firstname.lastname@example.org wrote:
> see here: http://stackoverflow.com/questions/9368783/cygwin-bash-sed-locks-my-files
> When I change files in cygwin bash with the sed command, the file gets locked.
> Open cmd and cd to non-user directory (f.e. temp)
> echo aaa > test.txt
> Open in texteditor, add line, try to save => works
> %CYGWIN_HOME%\bin\bash -c "sed -i 's/aaa/bbb/' test.txt
> In texteditor, add another line and try to save => "Access denied"
I just had a quick look into the aforementioned thread on stackoverflow.
The answers are a bit off the track. The problem here is that you mix
Windows and Cygwin tools in a directory with weird default permissions
which don't translate nicely to POSIX permissions.
Here's what happens:
- cmd's echo will create the file with default inherited Windows
permission bits. These permission bits don't make a lot of sense
from a POSIX point of view. That's where the ---------+ permissions
come from. That doesn't mean that you have no permissions! Note
the + at the end which means, there's an ACL with additional
permissions attached to the file. Use getfacl(Cygwin) or cacls(Windows)
to print the extra ACEs.
- Now you call Cygwin's sed to do in-place editing. The in-place
editing works like this:
- Create temporary file.
- write output to temporary file.
- Remove original file.
- Move temp file to original file
- Restore permissions from original file *in a POSIXy way*. I don't
know exactly how sed does that.
The problem here are the default permissions on the directory you're
calling CMD's echo in the first place. If you don't want to change them,
make sure that Cygwin ignores the permissions entirely and only fakes
POSIX permissions on that directory. That's what the "noacl" mount
option is for: http://cygwin.com/cygwin-ug-net/using.html#mount-table
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
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