[GRASS-dev] trying to set environment vars from a C program

[Glynn Clements]

Benjamin Ducke wrote:

> I am working on a set of modules to integrate GRASS with R.
> For this I need to read and set some global variables for R scripts to
> use.
> I would like to use shell environment variables for this and
> set them through a C module.
> However, if I use the C function setenv() in program foo.c, it seems to
> only add variables to the environment of foo.c.
> When foo.c terminates, all variables set with senenv() will be gone.
> 
> I have not found a way to modify the environment of the shell that
> starts foo.c so that the new variables will be available in the calling
> shell after foo.c has exited.
> 
> Is this somehow possible

No. One process cannot modify the environment of another process
(other than by directly modifying that process' address space, which
isn't really a viable option).

That's why export (sh) and setenv (csh) are shell built-in functions;
a separate program wouldn't work.

> or will I have to fall back to storing variables and values in an
> ASCII file?

That's why GRASS has $GISRC for "GRASS variables", i.e. so that you
can have programs which record information for subsequent use by other
programs.

-- 
Glynn Clements <glynn at gclements.plus.com>