Setting environment variables within a C program.

[Don Libes]

Since no one has posted a better reply than "no, you can't" let me
point out something.

I think what was wanted was a way to change environment variables in
the environment of the current process (and hence child processes).
The reason I think this, is because I have to do the same thing (see
last paragraph).  Obviously there is no way to change them in the
parent process.

I don't know the "right" way, but one way is to copy the environ array
pointers into a new array and make your change.  The reason you have to
use a new array is in case the change you are making adds a variable to
the environment.  If you are only resetting a variable, you just
reassign that one pointer to the variable value.  The reason this is
kludgey, of course, is that the space from the original environ becomes
unusable garbage.  That is, I haven't the faintest idea how to return
it (i.e.  free) to useful life.

I actually wrote a routine to do just this, so I know it works.  The
problem was on our Suns, I wanted to be able to create "tools" in
different fonts.  The only way you can do this is by setting the
environment variable DEFAULT_FONT.  Obviously, if you are controlling
the desktop with a C program (the window manager), then, you need to
set environment variables.

I'd be interested if someone could tell me the "right" way to do this.
I'd also like to know why fonts are selected via an environment
variable on the Sun.

Don Libes	{seismo,umcp-cs}!nbs-amrf!libes