modulefiles

Modulefiles are scripts used by the Environment Modules package to manage user environments on shared computing systems. They provide a mechanism to switch between different software packages and versions by applying environment changes when a module is loaded. A module load operation typically modifies PATH, LD_LIBRARY_PATH, MANPATH, and other variables, allowing multiple toolchains to coexist without conflicts.

Modulefiles are stored in directories referenced by MODULEPATH. Each modulefile defines changes via commands such as setenv, prepend-path, append-path, and dependencies like depends or prereq. Modulefiles can be written in Tcl for the original Modules, or in Lua for Lmod. They may include help text and metadata, and may declare conflicts or prerequisites to control loading behavior.

Users interact with a module command family: module avail lists loadable modules, module load name/version loads it, module list shows current loaded modules, module show name previews the changes. The module system is widely used in HPC clusters and data centers to simplify software stacks and improve reproducibility. Variants such as Lmod provide more scalable, lazy-loading and Python-friendly features, while classic Environment Modules use Tcl-based modulefiles.