PATH
variable tells the shell where to find those files.
Modern TeX implementations come with a bunch of search paths
built in to them. In most circumstances these paths are adequate, but
one sometimes needs to extend them to pick up files in strange
places: for example, we may wish to try a new bundle of packages
before installing them ‘properly’. To do
this, we need to change the relevant path as TeX perceives it.
However, we don’t want to throw away TeX’s built-in path (all of a
sudden, TeX won’t know how to deal with all sorts of things).
To extend a TeX path, we define an operating system
environment variable in ‘path format’, but leaving a gap which TeX
will fill with its built-in value for the path. The commonest case is
that we want to place our extension in front of the path, so that our
new things will be chosen in preference, so we leave our ‘gap to be
filled’ at the end of the environment variable. The syntax is simple
(though it depends which shell you’re actually using): so on a
Unix-like system, using the bash shell, the job might be
done like:
export TEXINPUTS=/tmp:
while in a Windows system, within a MSDOS window, it would be:
set TEXINPUTS=C:/temp;
In either case, we’re asking TeX to load files from the root disc
temporary files directory; in the Unix case, the “empty slot” is
designated by putting the path separator ‘:
’ on its own at the end
of the line, while in the Windows case, the technique is the same, but
the path separator is ‘;
’.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=tempinst