[GRASS-dev] Question regarding GRASS_NOTIFY

[Glynn Clements]

Nicklas Larsson via grass-dev wrote:

> Is there anyone out there who know about usage of the environment
> variable GRASS_NOTIFY, historically and in the present?

It's an external interface; it isn't used internally.

The intention is described in the email you cited: to allow a program
(specifically, ximgview or similar) to be notified of any changes to
the image file generated by the display library. It isn't required by
the GUI because the GUI can assume that the image will only be
modified by d.* commands which the GUI itself runs, so it can refresh
the view upon their completion.

The idea was to support the use of d.* commands from a shell,
providing something similar to the "monitor" system that was being
replaced at the time. I've have no idea whether such usage is still
common or even officially supported (but scripts/wxpyimgview is still
there).

> In addressing an otherwise trivial compiler warning, I stumbled into
> this for me strange piece of code and usage of GRASS_NOTIFY in the
> Raster Display Library. I put up a PR [1] suggesting the removal of
> this, but I agree with Vaclav I’d better ask here on the ML.
> 
> The only use of GRASS_NOTIFY is in “D_close_driver()” [2] and the
> value of that env variable (if set) is directly inserted in a
> “system()” call, without any sanitation!

What sort of "sanitisation" would you suggest? The variable is set by
the user, its value is passed directly to the shell.