[Lmod-users] Lmod 7.6.14: Reference counting for path like variables

[Robert M. <mc...@ta...>]

The latest version of Lmod now support reference counting for path-like
variables when Lmod is configured normally.  That is
$LMOD_DUPLICATE_PATHS=no (which is the default).

The documentation for PATH-like variables can be found here:

       http://lmod.readthedocs.io/en/latest/077_ref_counting.html

This reference counting means that if your original PATH is:

    export PATH=/usr/bin:/bin:/usr/local/bin

And a module FOO contains:

    append_path("PATH","/usr/local/bin")

then doing:

    $ module load FOO

Lmod will have

      PATH=/usr/bin:/bin:/usr/local/bin

but it remembers that /usr/local/bin has been added twice.  So unloading
FOO will keep

    PATH=/usr/bin:/bin:/usr/local/bin

But the reference count on /usr/local/bin goes to one.  This is different
that earlier behavior. Unloading the FOO module would have remove
/usr/local/bin from $PATH.

This is a new feature in Lmod but it is not a new feature in Env. Modules.
The pure TCL version of Tmod has had reference counting for path-like
variables for years.

-------------------------------------------------------
Special treatment for $MODULEPATH
-------------------------------------------------------

The MODULEPATH environment variable is treated special. No duplicates
entries are ever allowed. Also there no reference counting for PATH entries
stored in $MODULEPATH. Adding the same directory to $MODULEPATH will not
effect the reference count. It is always 1. This way a user can always
clear $MODULEPATH with:

    $ module unuse $MODULEPATH


Please test out this new version if you get the chance.  The version 7.6.14
is likely to become Lmod 7.7.

Thanks,
R.




-- 
Robert McLay, Ph.D.
TACC
Manager, HPC Software Tools
(512) 232-8104