On Wed, Jul 22, 2009 at 10:16:34PM -0500, _sc_ wrote:
>
> On Wednesday 22 July 2009 9:53 pm, Chris Sutcliffe wrote:
> >
> > >> Is it possible to clear an environment variable via vim script? I've
> > >> tried:
> > >>
> > >> let $MvVar =
> > >>
> > >> but vim complains. I've also tried:
> > >>
> > >> unlet $MyVar
> > >>
> > >> with no success.
> > >
> > > did you define MyVar with a dollar sign? or are you suffering from
> > > iknowtoomanylanguagesitus?
> >
> > It's an environmental variable that exists outside of Vim. What I
> > would like to do is clear it temporarily, call and external program,
> > and restore it after calling the external program. Something like:
> >
> > let save_MyVar = $MyVar
> > unlet $MyVar
> > exe '!someprog'
> > let $MyVar = save_MyVar
> >
> > would be ideal, but the 'unlet' is the problem.
>
> apparently i didn't have enough coffee this morning -- you did
> indeed say it was an environment variable
>
> since let and unlet are vim script commands, they affect variables
> inside the script, not the environment
>
> because '!' creates a new shell to run someprog, even if you
> execute '!export MyVar=' your next '!someprog' is going to get yet
> another shell to run in, and MyVar will be in its defined state
>
> one of the oldest Laws of Unix is no script can modify its parent's
> environment
>
> my recommendation is to write a new shell script that undefines
> MyVar and triggers someprog so vim doesn't have to care about shell
> environment variables -- or tweak someprog so it doesn't use MyVar
>
> sc
I don't quite agree. I don't think the orignal post is asking to modify
the parent's environment, just the spawned children's.
Although vim provides a mechanism to add environment variables,
it does not seem to provide any mechanism to remove environment
variables, whether or not it was created within vim. This is an
omission IMHO.
One may create an entirely new environment variable, that is passed to
children, with:
:let $NEWVAR = "foobar"
but there us no way to delete that environment variable. You can assign
a blank string to it,
:let $NEWVAR = ""
but that still leaves the variable in the environment.
IMHO,
:unlet $NEWVAR
should remove that environment variable completely. But it comes up as
error E488.
--
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Gregory H. Margo
gmargo at yahoo/com, gmail/com, pacbell/net; greg at margofamily/org
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