Environment Modules: provides dynamic modification of a user's environment
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Modules, provides dynamic modification of a user's environment

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The Modules package is a tool that simplify shell initialization and lets users easily modify their environment during the session with modulefiles.

Each modulefile contains the information needed to configure the shell for an application. Once the Modules package is initialized, the environment can be modified on a per-module basis using the module command which interprets modulefiles. Typically modulefiles instruct the module command to alter or set shell environment variables such as PATH, MANPATH, etc. modulefiles may be shared by many users on a system and users may have their own collection to supplement or replace the shared modulefiles.

Modules can be loaded and unloaded dynamically and atomically, in an clean fashion. All popular shells are supported, including bash, ksh, zsh, sh, csh, tcsh, fish, as well as some scripting languages such as tcl, perl, python, ruby, cmake and r.

Modules are useful in managing different versions of applications. Modules can also be bundled into metamodules that will load an entire suite of different applications.

Quick examples

Here is an example of loading a module on a Linux machine under bash.

$ module load gcc/6.1.1
$ which gcc
$ /usr/local/gcc/6.1.1/linux-x86_64/bin/gcc

Now we'll switch to a different version of the module

$ module switch gcc gcc/6.3.1
$ which gcc

And now we'll unload the module altogether

$ module unload gcc
$ which gcc
gcc not found

Now we'll log into a different machine, using a different shell (tcsh).

% module load gcc/6.3.1
% which gcc

Note that the command line is exactly the same, but the path has automatically configured to the correct architecture.

Getting things running

To learn how to install modules see INSTALL.txt for Unix system or INSTALL-win.txt for Windows

To have things running efficiently you will need a lot of additional setup. For an example take a look at doc/example.txt which explains how things have been setup at the University of Minnesota computer science department.


  • Tcl >= 8.4


Modules is distributed under the GNU General Public License version 2 (GPL v2). Read the file COPYING.GPLv2 for details.


Look at NEWS for summarized information regarding the changes brought by each released version. Look at ChangeLog for detailed information regarding changes.

The doc directory contains both the paper and man pages describing the user's and the module writer's usage. To generate the documentation files, like the man pages (you need Sphinx >= 1.0 to build the documentation), just type:

$ ./configure
$ make -C doc all

The following man pages are provided:

module(1), modulefile(4)

Test suite

Regression testing scripts are available in the testsuite directory (you need dejagnu to run the test suite):

$ ./configure
$ make test

Once modules is installed after running make install, you have the ability to test this installation with:

$ make testinstall

Transition from v3.2

Starting from v4.0, the Modules project provides the module command based on the native Tcl implementation as main version instead of the traditional C version. The full Tcl rewrite of the Modules package, previously called Modules-Tcl, was started in 2002 and has now reached maturity to take over the binary version in order to push forward the module concept.

All new releases are in fact double-releases as they also ship the latest stable version of the traditional C flavor of modulecmd. This compatibility version is labeled 3.2.11 as it is based on 3.2.10 with addition of widely used patches. The compatibility version builds and installs by default along with the new main version (v4 or later). Same initialization scripts are shared between compatibility and new main versions and a switchml shell function enables to swap from one module flavor to another.

If you are moving from Modules 3.2 to 4.0 or later, please look at the MIGRATING document. It provides an outlook of what has changed between the 2 versions. Both v3.2 and >=v4.0 are quite similar and transition to the new major version should be smooth. Slights differences may however be noticed in a few use-cases and the migration guide provides details about them.


Web site:


Online documentation:


GitHub source respository:


GitHub Issue tracking system:


SourceForge project page:



Current core developers and maintainers are:

The following people have notably contributed to Modules and Modules would not be what it is without their contributions:

  • Mark Lakata
  • Harlan Stenn
  • Leo Butler
  • Robert Minsk
  • Jens Hamisch
  • Peter W. Osel
  • John L. Furlani