Write a module file¶

A module file is a short text file that sets the environment for one package. Write one for software you installed yourself, such as a package built under your home directory or a Miniconda, so that one module load line puts it on your path in a session or a job, in either shell.

Module files are written in Tcl, and most need three or four lines. The first line must be #%Module1.0, and the rest set or extend environment variables. man modulefile lists every command.

Write the file¶

1. Create a directory for your module files:

   mkdir -p ~/modulefiles
   

2. Write the file, named for the package. To put a Miniconda installation on the path:

   ~/modulefiles/miniconda

   #%Module1.0
   prepend-path PATH /home/USERNAME/miniconda3/bin
   

   To add a library directory:

   ~/modulefiles/geos

   #%Module1.0
   prepend-path LD_LIBRARY_PATH /home/USERNAME/geos/lib
   

   To set several variables from one base directory:

   ~/modulefiles/crunch

   #%Module1.0
   set base /home/USERNAME/crunch
   prepend-path PATH $base/bin
   prepend-path LD_LIBRARY_PATH $base/lib
   setenv CRUNCH $base
   

   set makes a Tcl variable, used only inside the file. setenv exports a variable to the shell. prepend-path puts the directory first, append-path last. remove-path, unsetenv, conflict and module load are the other commands used in practice.

3. Load it by path and check the result:

   $ module load ~/modulefiles/crunch
   $ echo $CRUNCH
   /home/USERNAME/crunch
   

Load it by name¶

1. Tell the module command where your files are, once, with a ~/.modulerc file:

   ~/.modulerc

   #%Module1.0
   module use --append /home/USERNAME/modulefiles
   

2. Load by name from then on, in sessions and in job files:

   module load crunch
   

The system module files are under /share/apps/modulefiles and are the best examples of what a module file can do. module show NAME prints what any of them does.

Last updated 2026-10-03