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Lmod design

The style of variables is: varT: a table varA: an array

Spider

Spider searches for module(names). There are 3 levels of spider:

  • level 0: just list all modules, no input given
  • level 1: search for a module with a given name
  • level 2: search for a module with a given name/version

Level 2 will show how to load the specified module in a hierarchy.

canonical: the version according to Lmod Version: the version specify by whatis in the module (can be anything) pv: Python version (used to determine the latest version) wv: weighted version (user, system and module locale .modulerc) luaExt: location of the .lua in the filename (zero when tcl module)

MainControl

The MainControl is the heart of Lmod. An 'action' in a module file like setenv('foo', 'bar') has a different meaning depending on the mode. For a load it will set foo while for a unload it will delete it. There are 7 modes in Lmod:

  • Load
  • Unload
  • Access: for help and whatis messages
  • CheckSyntax: check if the module file is a valid module (a dummy run)
  • ComputeHash: generate a hash value for the contents of the module
  • DependencyCk: check if all 'depends_on' are still valid after a unload
  • MgrLoad: for a collection restore (loads are ignored)
  • Refresh: reloads the modules to make sure all shell functions and aliases are defined
  • Show: show the contents of the module
  • Spider: process module files for spider operations

The file MainControl.lua holds all code and the files MC_<mode>.lua assign what each action in a module exactly does.

The object MCP (MainControl Program) is created once and always points to a 'positive' action (a load basically). The lowercase mcp points to the current MainControl Program. These variables are global.

The file Hub.lua is were the real work is being done. MainControl will decides which functions get called from this file.

General flow

The Lmod main is in lmod.lua.in. There the MainControl Program (MCP) object is created. The array lmodCmdA does the translation between user input and a Lmod command. The file cmdfuncs.lua holds all 'user' actions. The main will run a function from that file which will call MainControl which calls Hub (or sometimes Hub directly).