Re: Using Zsh on a embedded system to configure GPIOs

[Mikael Magnusson <mikachu@gmail.com>]

On Sat, Nov 29, 2014 at 8:35 PM, Bart Schaefer
<schaefer@brasslantern.com> wrote:
> On Nov 29, 10:10am, meino.cramer@gmx.de wrote:
> }
> } To overwrite files I need to use ">!" instead of ">".
> }
> } Is there any way to automate this feature NOT to hit on my fingers,
> } if I want to write to files below /sys, /proc,, /dev...or
> } (better) to recognize, if such a file is a virtual one?
>
> I confess to being confused by the phrase "to hit on my fingers" ...
> but I think I can answer anyway.
>
> The HIST_ALLOW_CLOBBER option replaces ">" with ">|" in the history,
> so that if you forget to use the clobbering form all you need to do
> is recall the previous command with "!!" or the line editor.  Does
> that help?
>
> NO_CLOBBER already behaves differently for non-regular files, so that
> you can do things like "print foo > /dev/pts/3" without having to use
> ">|" (though that won't work for /dev/tty for a different reason).
>
> So if there is some way to identify a "virtual file" e.g. with stat(),
> that could potentially also be handled.  However, I think virtual files
> masquerade pretty thoroughly as real ones except for the fact that they
> appear to have size 0 yet contents can still be read.
>
> I suppose that, since the point of NO_CLOBBER is to prevent destroying
> existing file contents, redirection could be allowed to succeed for
> existing zero-sized files, which would then work for virtual files.
>
> However, that's not the way it works now, and zsh-workers would need to
> have some discussion of whether that change is acceptable.

Maybe we could add a NO_DESTRUCTIVE_CLOBBER which allows >> to
nonexisting files, > to zero sized files and possible etceteras, but
not > to nonzero files? I personally never find `>> nonexist` aborting
to be useful.

-- 
Mikael Magnusson