Expose procedures and variables to modulefiles

Same piece of code may be relevant for multiple modulefiles in your setup. Sharing code (procedures and variables) is preferred to redefining it in each modulefile. The following recipe describes an efficient way to define Tcl procedures and variables that will be then available from the modulefile evaluation context.


To expose site-specific procedures and variables across all modulefiles during their evaluation a site-specific configuration script is proposed.

This script exposes registered procedures to the Tcl interpreters that evaluate either modulerc or modulefile scripts.

By using the env global array, which holds environment variables, variables could also be exposed to those Tcl interpreters. Variables exposed this way, will be found set within modulefile or modulerc evaluation context but will not be exported to the environment changes the modulecmd.tcl script produces.

# append site-specific procedures referenced in the g_siteProcsToExposeToItrp
# variable defined below to the list of procedures exposed in the modulefile
# and modulerc evaluation interpreters
proc addSiteProcsToItrpAliasList {itrpaliasvname keyname args} {
   # ensure this proc is only called once at itrpaliasvname initialization
   trace remove variable $itrpaliasvname write addSiteProcsToItrpAliasList
   upvar #0 $itrpaliasvname itrpaliasv
   # register each site-specific procedure
   foreach procname $::g_siteProcsToExposeToItrp {
      if {$keyname ne {}} {
         set itrpaliasv($procname) $procname
      } else {
         lappend itrpaliasv $procname $procname
trace add variable ::g_modfileBaseAliases write addSiteProcsToItrpAliasList
trace add variable ::g_modrcAliases write addSiteProcsToItrpAliasList

# Define here site-specific procedures that should be exposed to modulefile
# and modulerc interpreter contexts
# *Beware* not to override an existing procedure of modulecmd.tcl script
proc mysiteproc {} {
   return sitevalue

# list all site-specific procedures to expose to modulefile and modulerc
# interpreter contexts
set g_siteProcsToExposeToItrp [list mysiteproc]

# Define here site-specific variables that should be exposed to modulefile
# and modulerc interpreter contexts. Use environment variable env array to
# transmit these variables
# *Beware* not to override an existing environment variable
set env(mysitevar) sitevarvalue

Compatible with Modules v4.2+


Create site-specific configuration directory if it does not exist yet:

$ mkdir /etc/environment-modules

Then copy there the site-specific configuration script of this recipe:

$ cp example/expose-procs-vars-to-modulefiles/siteconfig.tcl /etc/environment-modules/


Defined location for the site-specific configuration script may vary from one installation to another. To determine the expected location for this file on your setup, check the value of the siteconfig option on Modules version 4.3 or above:

$ module config siteconfig

On older version of Modules, check the modulecmd.tcl script:

$ grep '^set g_siteconfig ' $MODULES_CMD

The configuration script proposed should then be adapted to your needs:

  • define your own procedures
  • register them into the g_siteProcsToExposeToItrp list variable to expose them to the modulefile and modulerc evaluation contexts
  • define your own variables using the env array variable

Usage example

Enable the modulepath where the example modulefiles are located:

$ module use example/expose-procs-vars-to-modulefiles/modulefiles

Display one of the example modulefiles that makes use of the site-specific procedure and variable defined in the siteconfig.tcl script:

$ module show foo

setenv          FOO1 sitevalue
setenv          FOO2 sitevarvalue

Load one example modulefile and check that the environment variable it defines, which rely on the site-specific procedure and variable, are well set:

$ module load bar
$ echo $BAR1
$ echo $BAR2