Re: environment variable

> Some years ago I had been experimenting with things like this and it
> worked indeed.  It didn't work with arbitrary variables, but in this
> case $HOME is part of the filename.

It works up to teTeX-2.0.2. Variables which the kpathsea library expands
correctly can be used.

  $ cd /tmp
  $ mkdir TEST
  $ echo 'foo=/tmp/TEST' > /tmp/texmf.cnf
  $ echo '\input $foo/test.tex\bye' > x.tex
  $ echo hi > /tmp/TEST/test.tex
  $ TEXMFCNF=.: /t/2.0.2/i/bin/i686-pc-linux-gnu/tex x
  This is TeX, Version 3.14159 (Web2C 7.4.5)
  (./x.tex (/tmp/TEST/test.tex) [1] )
  Output written on x.dvi (1 page, 208 bytes).
  Transcript written on x.log.

> I suppose that formerly the filename had been passed to a shell (which
> expanded $HOME) and nowadays a system call is used instead.

No, it is not the shell but the kpathsea library. Olaf Weber says about it:

    Well, as far as I'm concerned the old implementation allowed this
    by accident, rather than design.  It should be an explicit feature,
    and (IMO) possible to turn it on and off.

Thomas