Re: [Xen-devel] [RFC PATCH 09/17] libxl: use \x1b to separate qemu arguments for linux stubdomain

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Wed, Aug 1, 2018 at 9:54 PM Simon Gaiser
<simon@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Simon Gaiser:
> > Marek Marczykowski-Górecki:
> >> On Wed, Aug 01, 2018 at 10:36:26AM -0400, Jason Andryuk wrote:
> >>> On Mon, Jul 30, 2018 at 11:56 PM, Marek Marczykowski-Górecki
> >>> <marmarek@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> >>>> This allows using arguments with spaces, like -append.
> >>>> Stubdomain side of this require "xenstore-client: Add option for raw
> >>>> in-/output" commit.
> >>>
> >>> I had to look up \x1b - it is ascii escape.  Since I was on the
> >>> www.asciitable.com, I saw \x1e is "record seperator" which might make
> >>> more sense.
> >>
> >> Simon, do you remember why you used \x1b? Otherwise indeed changing to
> >> \x1e would make sense.
> >
> > As far as I recall it's a mostly arbitrary choice. I think I choose 0x1b
> > because I thought that ASCII escape would be very unlikely to ever
> > appear in an cmdline. 0x00 would be even better but you don't want to
> > handle 0x00 in bash. I'm not aware of a problem with 0x1e.
>
> PS: If you follow the Wikipedia description [1] of the "separator"
> control characters 0x1f would fit even better. But I don't think it
> really matters what rare character we use.

Agreed. The choice shouldn't matter as long as it's a non-printable ascii char.

> [1]: https://en.wikipedia.org/wiki/C0_and_C1_control_codes#FS

Regards,
Jason

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