MIGRATING

This document describes the major changes occurring between versions of Modules. It provides an overview of the new features and changed behaviors that will be encountered when upgrading.

Migrating from v4.4 to v4.5

This new version is backward-compatible with v4.4 and primarily fixes bugs and adds new features.

New features

Version 4.5 introduces new functionalities that are described in this section.

ml command

The ml command is added to Modules. ml is a frontend to the module command that reduces the number of characters to type to trigger module actions.

With no argument provided ml is equivalent to module list, ml foo corresponds to module load foo and ml -foo means module unload foo:

$ ml foo
$ ml
Currently Loaded Modulefiles:
 1) foo/2
$ ml -foo
$ ml
No Modulefiles Currently Loaded.

Multiple modules to either load or unload can be combined on a single command. The unloads are first processed then the loads.

ml accepts all command-line switches and sub-commands accepted by module command:

$ ml avail -t foo
foo/1
foo/2

This handy interface has been originally developed by the Lmod project. Having this command line interface also supported on Modules helps to provide a similar user experience whatever the module implementation used.

JSON format output

The -j and --json command line switches are added for the avail, list, savelist, whatis and search module sub-commands. When set, the output result of these sub-commands is rendered in JSON format:

$ module avail --json bar | python -mjson.tool
{
    "/path/to/modulefiles": {
        "bar/2.3": {
            "name": "bar/2.3",
            "pathname": "/path/to/modulefiles/bar/2.3",
            "symbols": [
                "default"
            ],
            "type": "modulefile"
        },
        "bar/3.4": {
            "name": "bar/3.4",
            "pathname": "/path/to/modulefiles/bar/3.4",
            "symbols": [],
            "type": "modulefile"
        }
    }
}
$ ml whatis -j foo/1.2.3 | python -mjson.tool
{
    "/path/to/modulefiles": {
        "foo/1.2.3": {
            "name": "foo/1.2.3",
            "whatis": [
                "The foo/1.2.3 modulefile"
            ]
        }
    }
}

Improved Windows support

A new option to the ./configure script named --enable-windows-support is introduced to install additional files relative to the enablement of Modules on the Windows platform. When set, this option installs module.cmd, ml.cmd and envml.cmd scripts in bindir and initialization script cmd.cmd in initdir. With these four files the Modules installation may be used from either a Unix or a Windows platform.

module.cmd, ml.cmd and envml.cmd scripts respectively provide the module, ml and envml commands for Windows cmd terminal shell, relying on modulecmd.tcl script which was already able to produce shell code for this Windows shell. Initialization script cmd.cmd adds the directory of module.cmd, ml.cmd and envml.cmd to PATH.

These Windows-specific files are relocatable: module.cmd, ml.cmd and envml.cmd scripts expect to find initialization script cmd.cmd in the init directory next to them (to setup Modules-specific variables in current environment) and cmd.cmd expects modulecmd.tcl to be found in libexec directory and the 3 commands in bin directory next to it.

Starting from this 4.5 release a distribution zipball is published to install Modules on Windows. This zip archive ships an install and an uninstall scripts (INSTALL.bat and UNINSTALL.bat). The zipball can be built locally from Modules sources by running make dist-win.

The Installing Modules on Windows document describes how to install Modules on Windows from the distribution zipball.

Error stack trace

Error messages will now embed a stack trace for unknown errors to help localize the root cause of issues. This change applies to modulefile evaluation:

Loading foo/1.2
  Module ERROR: add-path cannot handle path equals to separator string
        while executing
    "append-path PATH :"
        (file "/path/to/modulefiles/foo/1.2" line 24)
    Please contact <root@localhost>

A stack trace is also returned when an unknown error occurs in modulecmd.tcl script, which facilitates issue report and analysis:

$ module load bar
ERROR: invalid command name "badcommand"
      while executing
  "badcommand"
      (procedure "module" line 14)
      invoked from within
  "module load bar"
      ("eval" body line 1)
      invoked from within
  "eval $execcmdlist"
  Please report this issue at https://github.com/cea-hpc/modules/issues

Automatic default and latest symbolic versions

When the implicit default mechanism and the Advanced module version specifiers are both enabled, a default and a latest symbolic versions are automatically defined for each module name.

This new feature gives the ability to select the highest version available for a module, without knowing beforehand this version name:

$ module load -v [email protected]
Loading foo/1.10

The symbolic versions are automatically defined unless a symbolic version, an alias or a regular module version already exists for these default or latest version names.

Further reading

To get a complete list of the changes between Modules v4.4 and v4.5, please read the Release notes document.

Migrating from v4.3 to v4.4

This new version is backward-compatible with v4.3 and primarily fixes bugs and adds new features.

Warning

Modules configuration option handling has been reworked internally to provide a unified way for all options to get initialized, retrieved or set. Existing site-specific configuration script should be reviewed to make use of the new getConf, setConf, unsetConf and lappendConf procedures to manipulate configuration options.

New features

Version 4.4 introduces new functionalities that are described in this section.

Specify modules in a case insensitive manner

The ability to match module name in a case insensitive manner has been added. This feature can be enabled at different level with the following values set to the icase configuration option:

  • never: a case sensitive match is applied in any cases
  • search: a case insensitive match is applied to the avail, whatis and paths sub-commands
  • always: a case insensitive match is applied to search contexts and also to the other module sub-commands and modulefile Tcl commands for the module specification they receive as argument.

It can help for instance to load a module without knowing the case used to name its relative modulefile:

$ module config icase always
$ module load -v mysoftware
Loading MySoftware/1.0

Insensitive case match activation can be controlled at configure time with the --with-icase option, which could be passed any of the above activation levels. This option could be superseded with the MODULES_ICASE environment variable, which could be set through the config sub-command with the icase option. Command-line switch --icase supersedes in turns any other icase configurations. When this command-line switch is passed, icase mode equals always.

Extended default

The extended default mechanism has been introduced to help selecting a module when only the first numbers in its version are specified. Starting portion of the version, part separated from the rest of the version string by a . character, could be used to refer to a more precise version number.

This mechanism is activated through the new configuration option extended_default. It enables to refer to a module named foo/1.2.3 as foo/1.2 or foo/1:

$ module config extended_default 1
$ module load -v foo/1
Loading foo/1.2.3

When multiple versions match partial version specified and only one module should be selected, the default version (whether implicitly or explicitly defined) among matches is returned. The following example shows that foo/1.1.1, the foo module default version, is selected when it matches query. Elsewhere the highest version (also called the latest version or the implicit default) among matching modules is returned:

$ module av foo
--------------- /path/to/modulefiles ---------------
foo/1.1.1(default)  foo/1.2.1  foo/1.10
foo/1.1.10          foo/1.2.3
$ module load -v foo/1.1
Loading foo/1.1.1
$ module purge
$ module load -v foo/1.2
Loading foo/1.2.3
$ module purge
$ module load -v foo/1
Loading foo/1.1.1

In case implicit_default option is disabled and no explicit default is found among matches, an error is returned:

$ module config implicit_default 0
$ module load -v foo/1.2
ERROR: No default version defined for 'foo/1.2'

When it is enabled, extended default applies everywhere a module could be specified, which means it could be used with any module sub-command or any modulefile Tcl command receiving a module specification as argument. It may help for instance to declare dependencies between modules:

$ module show bar/3
----------------------------------------------------------
/path/to/modulefiles/bar/3.4:

prereq              foo/1.2
----------------------------------------------------------
$ module load --auto bar/3
Loading bar/3.4
  Loading requirement: foo/1.2.3

Extended default activation can be controlled at configure time with the --enable-extended-default option. This option could be superseded with the MODULES_EXTENDED_DEFAULT environment variable, which could be set through the config sub-command with the extended_default option.

Advanced module version specifiers

The ability to specify finer constraints on module version has been added to Modules. It enables to filter the module selection to a given version list or range by specifying after the module name a version constraint prefixed by the @ character.

This new feature leverages the version specifier syntax of the Spack package manager as this syntax covers all the needs for a fine-grained selection of module versions. It copes very well with command-line typing, by avoiding characters having a special meaning on shells. Moreover the users of Spack that also are users of Modules may already be familiar with this syntax.

The mechanism introduced here is called advanced module version specifier and it can be activated through the new configuration option advanced_version_spec. Constraints can be expressed to refine the selection of module version to:

  • a single version with the @version syntax, for instance foo@1.2.3 syntax will select module foo/1.2.3
  • a list of versions with the @version1,version2,... syntax, for instance foo@1.2.3,1.10 will match modules foo/1.2.3 and foo/1.10
  • a range of versions with the @version1:, @:version2 and @version1:version2 syntaxes, for instance foo@1.2: will select all versions of module foo greater than or equal to 1.2, foo@:1.3 will select all versions less than or equal to 1.3 and foo@1.2:1.3 matches all versions between 1.2 and 1.3 including 1.2 and 1.3 versions

This new feature enables for instance to list available versions of module foo higher or equal to 1.2:

$ module config advanced_version_spec 1
$ module av foo
--------------- /path/to/modulefiles ---------------
foo/1.1.1(default)  foo/1.2.1  foo/1.10
foo/1.1.10          foo/1.2.3
$ module av [email protected]:
--------------- /path/to/modulefiles ---------------
foo/1.2.1  foo/1.2.3  foo/1.10

Then choose to load for instance a version higher than or equal to 1.2 and less than or equal to 1.3. Default version is selected if it corresponds to a version included in the range, elsewhere the highest version (also called latest version or implicit default) is selected:

$ module load -v [email protected]:1.3
Loading foo/1.2.3

In case implicit_default option is disabled and no explicit default is found among version specifier matches, an error is returned:

$ module config implicit_default 0
$ module load -v [email protected]:1.3
ERROR: No default version defined for '[email protected]:1.3'

When advanced module version specifier is enabled, it applies everywhere a module could be specified, which means it could be used with any module sub-command or any modulefile Tcl command receiving a module specification as argument. It may help for instance to declare smoother dependencies between modules:

$ module show [email protected]:2
----------------------------------------------------------
/path/to/modulefiles/bar/2.3:

prereq          [email protected],1.2.1
----------------------------------------------------------
$ module load --auto [email protected]:2
Loading bar/2.3
  Loading requirement: foo/1.2.1

Advanced specification of single version or list of versions may benefit from the activation of the Extended default mechanism (range of versions natively handles abbreviated versions):

$ module config extended_default 1
$ module load -v [email protected]
Loading foo/1.2.3
$ module unload -v foo @1.2,1.5
Unloading foo/1.2.3

Advanced module version specifier activation can be controlled at configure time with the --enable-advanced-version-spec option. This option could be superseded with the MODULES_ADVANCED_VERSION_SPEC environment variable, which could be set through the config sub-command with the advanced_version_spec option.

Further reading

To get a complete list of the changes between Modules v4.3 and v4.4, please read the Release notes document.

Migrating from v4.2 to v4.3

This new version is backward-compatible with v4.2 and primarily fixes bugs and adds new features.

New features

Version 4.3 introduces new functionalities that are described in this section.

Modulepath rc file

A .modulerc file found at the root of an enabled modulepath directory is now evaluated when modulepath is walked through to locate modulefiles. This modulepath rc file gives for instance the ability to define module alias whose name does not correspond to any module directory in this modulepath. Thus this kind of module alias would not be found unless if it is defined at the modulepath global scope.

Further I/O operations optimization

Additional work has been performed to save a significant number of filesystem I/O operations made to search and evaluate modulefiles.

When fully read, the content of a modulefile is now cached in memory to avoid new I/O operations in case this modulefile should be read one more time during the same module command evaluation.

Except for path, paths, list, avail and aliases module commands always fully read a modulefile whether its full content is needed or just its header to verify its validity. This way modulefiles are only read once on commands that first check modulefile validity then read again valid files to get their full content.

Last but not least, Modules Tcl extension library is introduced to extend the Tcl language in order to provide more optimized I/O commands to read a file or a directory content than native Tcl commands do. This library is built and enabled in modulecmd.tcl script with --enable-libtclenvmodules configure argument (it is enabled by default). As this library is written in C, it must be compiled and --with-tcl or --with-tclinclude configure arguments may be used to indicate where to find Tcl development files.

Modules Tcl extension library greatly reduces the number of filesystem I/O operations by removing unneeded ioctl, fcntl and lstat system calls done (by Tcl open command) to read each modulefile. Directory content read is also improved by fetching hidden and regular files in one pass. Moreover .modulerc and .version read access is tested only if these files are found in the directory.

Colored output

The ability to graphically enhance some part of the produced output has been added to improve readability. Among others, error, warning and info message prefixes can be colored as well as modulepath, module alias and symbolic version.

Color mode can be set to never, auto or always. When color mode is set to auto, output is colored only if the standard error output channel is attached to a terminal.

Default color mode could be controlled at configure time with the --enable-color and the --disable-color option, which respectively correspond to the auto and never color mode. This default mode could be superseded with the CLICOLOR, CLICOLOR_FORCE and MODULES_COLOR environment variables and the --color command-line switch.

Color to apply to each element can be controlled with the MODULES_COLORS environment variable or the --with-dark-background-colors and --with-light-background-colors configure options. These variable and options take as value a colon-separated list in the same fashion LS_COLORS does. In this list, output item that should be highlighted is designated by a key which is associated to a Select Graphic Rendition (SGR) code.

The MODULES_TERM_BACKGROUND environment variable and the --with-terminal-background configure option help Modules to determine if the color set for dark background or the color set for light background should be used to color output in case no specific color set is defined with the MODULES_COLORS variable.

Output items able to be colorized and their relative key are: highlighted element (hi), debug information (db), tag separator (se); Error (er), warning (wa), module error (me) and info (in) message prefixes; Modulepath (mp), directory (di), module alias (al), module symbolic version (sy), module default version (de) and modulefile command (cm).

For instance the default color set for a terminal with dark background is defined to:

hi=1:db=2:se=2:er=91:wa=93:me=95:in=94:mp=1;94:di=94:al=96:sy=95:de=4:cm=92

When colored output is enabled and a specific graphical rendition is defined for module default version, the default symbol is omitted and instead the defined graphical rendition is applied to the relative modulefile. When colored output is enabled and a specific graphical rendition is defined for module alias, the @ symbol is omitted.

CLICOLOR and CLICOLOR_FORCE environment variables are also honored to define color mode. The never mode is set if CLICOLOR equals to 0. If CLICOLOR is set to another value, it corresponds to the auto mode. The always mode is set if CLICOLOR_FORCE is set to a value different than 0. Color mode set with these two variables is superseded by mode set with MODULES_COLOR environment variable.

Configure modulecmd with config sub-command

The config sub-command has been added to module to help getting or setting the modulecmd.tcl options. With no additional command-line argument, this sub-command reports the current value of all existing options with a mention to indicate if this value has been overridden from a command-line switch or from an environment variable.

See the description of this sub-command in the module man page for a complete reference on existing configuration options.

Most of the options can be altered by passing the option name and a value to the sub-command. Setting an option by this mean overrides its default value, set at installation time in modulecmd.tcl script, by defining the environment variable which supersedes this default.:

$ module config auto_handling 1
$ module config auto_handling
Modules Release 4.3.0 (2019-07-26)

- Config. name ---------.- Value (set by if default overridden) ---------------
auto_handling             1 (env-var)

Setting options with module config could be done in the Modules initialization RC file to change default value of options when module command is initialized.

When command-line switch --reset and an option name is passed to the config sub-command, it restores default value for configuration option by unsetting related environment variable.

With command-line switch --dump-state, the config sub-command reports, in addition to currently set options, the current state of modulecmd.tcl script and Modules-related environment variables. Providing the output of the module config --dump-state command when submitting an issue to the Modules project will help to analyze the situation.

Control module command verbosity

The ability to control message verbosity has been added so module command can be configured whether it should display more or less information. Available verbosity levels from the least to the most verbose are:

  • silent: turn off error, warning and informational messages but does not affect module command output result.
  • concise: enable error and warning messages but disable informational messages.
  • normal: turn on informational messages, like a report of the additional module evaluations triggered by loading or unloading modules, aborted evaluation issues or a report of each module evaluation occurring during a restore or source sub-commands.
  • verbose: add additional informational messages, like a systematic report of the loading or unloading module evaluations.
  • debug: print debugging messages about module command execution.

Default verbosity level can be controlled at configure time with the --with-verbosity option, which could be passed any of the above level names. This default verbosity level could be superseded with the MODULES_VERBOSITY environment variable, which could be set through the config sub-command with the verbosity option. Command-line switches --silent, --verbose and --debug supersede in turns any other verbosity configuration to respectively set module command silent, verbose or in debug mode.

Other new sub-commands, command-line switches and environment variables

  • The avail sub-command gets two new command-line switches: --indepth and --no-indepth. These options control whether search results should recursively include or not modulefiles from directories matching search query. Shell completion scripts have been updated to complete available modulefiles in the no in depth mode.
  • The MODULES_AVAIL_INDEPTH environment variable defines if the avail sub-command should include or exclude by default the modulefiles from directories matching search query. Its value is superseded by the use of the --indepth and --no-indepth command-line switches.
  • The clear sub-command, which was available on Modules version 3.2, has been reintroduced. This sub-command resets the Modules runtime information but does not apply further changes to the environment at all. This sub-command now leverages the --force command-line switch to skip its confirmation dialog.
  • The MODULES_SITECONFIG environment variable defines an additional siteconfig script which is loaded if it exists after the siteconfig script configured at build time in modulecmd.tcl. This ability is enabled by default and could be disabled with configure option --with-locked-configs=extra_siteconfig.
  • The MODULES_UNLOAD_MATCH_ORDER environment variable sets whether the firstly or the lastly loaded module should be selected for unload when multiple loaded modules match unload request. Configure option --with-unload-match-order defines this setting which can be superseded by the environment variable. By default, lastly loaded module is selected and it is recommended to keep this behavior when used modulefiles express dependencies between each other.
  • The MODULES_IMPLICIT_DEFAULT environment variable sets whether an implicit default version should be defined for modules with no default version explicitly defined. When enabled, which is the default behavior, a module version is automatically selected (latest one) when the generic name of the module is passed. When implicit default is disabled and no default version is explicitly defined for a module, the name of this module to evaluate should be fully qualified elsewhere an error is returned. Configure option --enable-implicit-default defines this setting which can be superseded by the environment variable. This superseding mechanism can be disabled with configure option --with-locked-configs=implicit_default.
  • The MODULES_SEARCH_MATCH environment variable defines the matching style to perform when searching for available modules. With starts_with value, modules whose name begins by search query string are returned. When search match style is set to contains, modules returned are those whose fully qualified name contains search query string. Configure option --with-search-match defines this setting which can be superseded by the environment variable, which in turns can be superseded by the --starts-with and --contains command-line switches of avail module sub-command.
  • The MODULES_SET_SHELL_STARTUP environment variable controls whether or not shell startup file should be set to ensure module command is defined once shell has been initialized. When enabled, the ENV and BASH_ENV environment variables are set, when module function is defined, to the Modules bourne shell initialization script. Configure options --enable-set-shell-startup and --disable-set-shell-startup define this setting which can be superseded by the environment variable.
  • When initializing the module command in a shell session, initialization configuration files stored in the defined configuration directory are taken into account if present instead of the configuration files stored in the initialization script directory. When they are stored in the configuration directory, these configuration files are named initrc and modulespath instead of respectively modulerc and .modulespath. The location of the installation of those files can be controlled with configure option --with-initconf-in, which accepts etcdir and initdir values.
  • The MODULES_WA_277 environment variable helps to define an alternative module alias on Tcsh shell when set to 1. It workarounds an issue on Tcsh history mechanism occurring with default module command alias: erroneous history entries are recorded each time the module command is called. However the alternative definition of the module alias weakens shell evaluation of the code produced by modulefiles. Characters with special meaning for Tcsh shell (like { and }) may not be used anymore in shell alias definition elsewhere the evaluation of the code produced by modulefiles will return a syntax error.

Further reading

To get a complete list of the changes between Modules v4.2 and v4.3, please read the Release notes document.

Migrating from v4.1 to v4.2

This new version is backward-compatible with v4.1 and primarily fixes bugs and adds new features.

New features

Version 4.2 introduces new functionalities that are described in this section.

Modulefile conflict constraints consistency

With the conflict modulefile command, a given modulefile can list the other modulefiles it conflicts with. To load this modulefile, the modulefiles it conflicts with cannot be loaded.

This constraint was until now satisfied when loading the modulefile declaring the conflict but it vanished as soon as this modulefile was loaded. In the following example a modulefile declares a conflict with b:

$ module load b a
WARNING: a cannot be loaded due to a conflict.
HINT: Might try "module unload b" first.
$ module list
Currently Loaded Modulefiles:
 1) b
$ module purge
$ module load a b
$ module list
Currently Loaded Modulefiles:
 1) a   2) b

Consistency of the declared conflict is now ensured to satisfy this constraint even after the load of the modulefile declaring it. This is achieved by keeping track of the conflict constraints of the loaded modulefiles in an environment variable called MODULES_LMCONFLICT:

$ module load a b
ERROR: WARNING: b cannot be loaded due to a conflict.
HINT: Might try "module unload a" first.
$ module list
Currently Loaded Modulefiles:
 1) a

An environment variable is used to keep track of this conflict information to proceed the same way than used to keep track of the loaded modulefiles with the LOADEDMODULES environment variable.

In case a conflict constraint toward a modulefile is set by an already loaded modulefile, loading the conflicting modulefile will lead to a load evaluation attempt in order for this modulefile to get the chance to solve the constraint violation. If at the end of the load evaluation, the conflict has not been solved, modulefile load will be discarded.

Warning

On versions 4.2.0 and 4.2.1, a conflict constraint set by an already loaded modulefile forbade the load of the conflicting modulefile. This has been changed starting version 4.2.2 to better cope with behaviors of previous Modules version: an evaluation attempt of the conflicting modulefile is made to give it the opportunity to solve this conflict by using module unload modulefile command.

Modulefile prereq constraints consistency

With the prereq modulefile command, a given modulefile can list the other modulefiles it pre-requires. To load this modulefile, the modulefiles it pre-requires must be loaded prior its own load.

This constraint was until now satisfied when loading the modulefile declaring the prereq but, as for the declared conflict, it vanished as soon as this modulefile was loaded. In the following example c modulefile declares a prereq on a:

$ module load c
WARNING: c cannot be loaded due to missing prereq.
HINT: the following module must be loaded first: a
$ module list
No Modulefiles Currently Loaded.
$ module load a c
$ module list
Currently Loaded Modulefiles:
 1) a   2) c
$ module unload a
$ module list
Currently Loaded Modulefiles:
 1) c

Consistency of the declared prereq is now ensured to satisfy this constraint even after the load of the modulefile declaring it. This is achieved, like for the conflict consistency, by keeping track of the prereq constraints of the loaded modulefiles in an environment variable called MODULES_LMPREREQ:

$ module load a c
$ module list
Currently Loaded Modulefiles:
 1) a   2) c
$ module unload a
ERROR: WARNING: a cannot be unloaded due to a prereq.
HINT: Might try "module unload c" first.
$ module list
Currently Loaded Modulefiles:
 1) a   2) c

By-passing module defined constraints

The ability to by-pass a conflict or a prereq constraint defined by modulefiles is introduced with the --force command line switch (-f for short notation) for the load, unload and switch sub-commands.

With this new command line switch, a given modulefile is loaded even if it conflicts with other loaded modulefiles or even if the modulefiles it pre-requires are not loaded. Some example reusing the same modulefiles a, b and c than above:

$ module load b
$ module load --force a
WARNING: a conflicts with b
$ module list
Currently Loaded Modulefiles:
 1) b   2) a
$ module purge
$ module load --force c
WARNING: c requires a loaded
$ module list
Currently Loaded Modulefiles:
 1) c

--force also enables to unload a modulefile required by another loaded modulefiles:

$ module load a c
$ module list
Currently Loaded Modulefiles:
 1) a   2) c
$ module unload --force a
WARNING: a is required by c
$ module list
Currently Loaded Modulefiles:
 1) c

In a situation where some of the loaded modulefiles have unsatisfied constraints corresponding to the prereq and conflict they declare, the save and reload sub-commands do not perform and return an error.

Automated module handling mode

An automatic management of the dependencies between modulefiles has been added and it is called automated module handling mode. This new mode consists in additional actions triggered when loading or unloading a modulefile to satisfy the constraints it declares.

When loading a modulefile, following actions are triggered:

  • Requirement Load (ReqLo): load of the modulefiles declared as a prereq of the loading modulefile.
  • Dependent Reload (DepRe): reload of the modulefiles declaring a prereq onto loaded modulefile or declaring a prereq onto a modulefile part of this reloading batch.

When unloading a modulefile, following actions are triggered:

  • Dependent Unload (DepUn): unload of the modulefiles declaring a non-optional prereq onto unloaded modulefile or declaring a non-optional prereq onto a modulefile part of this unloading batch. A prereq modulefile is considered optional if the prereq definition order is made of multiple modulefiles and at least one alternative modulefile is loaded.
  • Useless Requirement Unload (UReqUn): unload of the prereq modulefiles that have been automatically loaded for either the unloaded modulefile, an unloaded dependent modulefile or a modulefile part of this useless requirement unloading batch. Modulefiles are added to this unloading batch only if they are not required by any other loaded modulefiles. MODULES_LMNOTUASKED environment variable helps to keep track of these automatically loaded modulefiles and to distinguish them from modulefiles asked by user.
  • Dependent Reload (DepRe): reload of the modulefiles declaring a conflict or an optional prereq onto either the unloaded modulefile, an unloaded dependent or an unloaded useless requirement or declaring a prereq onto a modulefile part of this reloading batch.

In case a loaded modulefile has some of its declared constraints unsatisfied (pre-required modulefile not loaded or conflicting modulefile loaded for instance), this loaded modulefile is excluded from the automatic reload actions described above.

For the specific case of the switch sub-command, where a modulefile is unloaded to then load another modulefile. Dependent modulefiles to Unload are merged into the Dependent modulefiles to Reload that are reloaded after the load of the switched-to modulefile.

This automated module handling mode integrates concepts (like the Dependent Reload mechanism) of the Flavours extension, which was designed for Modules compatibility version. As a whole, automated module handling mode can be seen as a generalization and as an expansion of the Flavours concepts.

This new feature can be controlled at build time with the --enable-auto-handling configure option. This default configuration can be superseded at run-time with the MODULES_AUTO_HANDLING environment variable or the command line switches --auto and --no-auto.

By default, automated module handling mode is disabled and will stay so until the next major release version (5.0) where it will be enabled by default. This new feature is currently considered experimental and the set of triggered actions will be refined over the next feature releases.

Consistency of module load/unload commands in modulefile

With the module load modulefile command, a given modulefile can automatically load a modulefile it pre-requires. Similarly with the module unload modulefile command, a given modulefile can automatically unload a modulefile it conflicts with.

Both commands imply additional actions on the loaded environment (loading or unloading extra modulefiles) that should cope with the constraints defined by the loaded environment.

Additionally module load and module unload modulefile commands express themselves constraints on loaded environment that should stay satisfied to ensure consistency.

To ensure the consistency of module load modulefile command once the modulefile defining it has been loaded, this command is assimilated to a prereq command. Thus the defined constraint is recorded in the MODULES_LMPREREQ environment variable. Same approach is used for module unload modulefile command which is assimilated to a conflict command. Thus the defined constraint is recorded in the MODULES_LMCONFLICT environment variable.

To ensure the consistency of the loaded environment, the additional actions of the module load and module unload modulefile commands have been adapted in particular situations:

  • When unloading modulefile, module load command will unload the modulefile it targets only if no other loaded modulefile requires it and if this target has not been explicitly loaded by user.
  • When unloading modulefile, module unload command does nothing as the relative conflict registered at load time ensure environment consistency and will forbid conflicting modulefile load.

Please note that loading and unloading results may differ than from previous Modules version now that consistency is checked:

  • Modulefile targeted by a module load modulefile command may not be able to load due to a registered conflict in the currently loaded environment. Which in turn will break the load of the modulefile declaring the module load command.
  • Modulefile targeted by a module unload modulefile command may not be able to unload due to a registered prereq in the loaded environment. Which in turn will break the load of the modulefile declaring the module unload command.
  • If automated module handling mode is enabled, module load modulefile command is interpreted when unloading modulefile as part of the Useless Requirement Unload (UReqUn) mechanism not through modulefile evaluation. As a consequence, an error occurring when unloading the modulefile targeted by the module load command does not break the unload of the modulefile declaring this command. Moreover unload of the module load targets is done in the reverse loaded order, not in the module load command definition order.

Modulefile alias and symbolic modulefile name consistency

With the module-alias and module-version modulefile commands, alternative names can be given to a modulefile. When these names are used to load for instance a modulefile, they are resolved to the modulefile they target which is then processed for the load action.

Until now, the alias and symbolic version names were correctly resolved for the load and unload actions and also for the querying sub-commands (like avail or whatis). However this alternative name information vanishes once the modulefile it resolves to is loaded. As a consequence there was no consistency over these alternative designations. In the following example f modulefile declares a conflict on e alias which resolves to d modulefile:

$ module load e
$ module list
Currently Loaded Modulefiles:
 1) d
$ module info-loaded e
$ module load f
$ module list
Currently Loaded Modulefiles:
 1) d   2) f

Consistency of the alternative names set on a modulefile with module-alias and module-version commands is now ensured to enable modulefile commands prereq, conflict, is-loaded and module-info loaded using these alternative designations as argument. This consistency is achieved, like for the conflict and prereq consistencies, by keeping track of the alternative names of the loaded modulefiles in an environment variable called MODULES_LMALTNAME:

$ module load e
$ module list
Currently Loaded Modulefiles:
 1) d
$ module info-loaded e
d
$ module load f
WARNING: f cannot be loaded due to a conflict.
HINT: Might try "module unload e" first.
$ module list
Currently Loaded Modulefiles:
 1) d

Environment variable change through modulefile evaluation context

All environment variable edition commands (setenv, unsetenv, append-path, prepend-path and remove-path) have been updated to:

  • Reflect environment variable value change on the environment of the current modulefile Tcl interpreter. So using $env(VAR) will return the currently defined value for environment variable VAR, not the one found prior modulefile evaluation.
  • Clear environment variable content instead of unsetting it on the environment of the current modulefile Tcl interpreter to avoid raising error about accessing an undefined element in $env(). Code is still produced to purely unset environment variable in shell environment.

Exception is made for the whatis evaluation mode: environment variables targeted by variable edition commands are not set to the defined value in the evaluation context during this whatis evaluation. These variables are only initialized to an empty value if undefined. This exception is made to save performances on this global evaluation mode.

Improved module message report

Module sub-commands like load, unload or switch, may perform multiple load or unload modulefile evaluations in a row. Also these kind of evaluation modes may sometimes trigger additional load or unload evaluations, when for instance a modulefile contains a module load command.

To improve the readability of the module messages produced relatively to a load or an unload evaluation, these messages are now stacked under a Loading or an Unloading message block that gathers all the messages produced for a given modulefile evaluation:

$ module load --no-auto foo
Loading foo/1.2
  ERROR: foo/1.2 cannot be loaded due to missing prereq.
    HINT: the following module must be loaded first: bar/4.5

In addition, foreground load, unload, switch and restore actions (ie. asked on the command-line) now report a summary of the additional load and unload evaluations that were eventually triggered in the process:

$ module load --auto foo
Loading foo/1.2
  Loading requirement: bar/4.5

New modulefile commands

2 new modulefile Tcl commands have been introduced:

  • set-function: define a shell function on sh-kind and fish shells.
  • unset-function: unset a shell function on sh-kind and fish shells.

Further reading

To get a complete list of the changes between Modules v4.1 and v4.2, please read the Release notes document.

Migrating from v4.0 to v4.1

This new version is backward-compatible with v4.0 and primarily fixes bugs and adds new features.

New features

Version 4.1 introduces a bunch of new functionalities. These major new features are described in this section.

Virtual modules

A virtual module stands for a module name associated to a modulefile. The modulefile is the script interpreted when loading or unloading the virtual module which appears or can be found with its virtual name.

The module-virtual modulefile command is introduced to give the ability to define these virtual modules. This new command takes a module name as first argument and a modulefile location as second argument:

module-virtual app/1.2.3 /path/to/virtualmod/app

With this feature it is now possible to dynamically define modulefiles depending on the context.

Extend module command with site-specific Tcl code

module command can now be extended with site-specific Tcl code. modulecmd.tcl now looks at a siteconfig.tcl file in an etcdir defined at configure time (by default $prefix/etc). If it finds this Tcl script file, it is sourced within modulecmd.tcl at the beginning of the main procedure code.

siteconfig.tcl enables to supersede any global variable or procedure definitions made in modulecmd.tcl with site-specific code. A module sub-command can for instance be redefined to make it fit local needs without having to touch the main modulecmd.tcl.

Quarantine mechanism to protect module execution

To protect the module command run-time environment from side effect coming from the current environment definition a quarantine mechanism is introduced. This mechanism, sets within module function definition and shell initialization script, modifies the modulecmd.tcl run-time environment to sanitize it.

The mechanism is piloted by environment variables. First of all MODULES_RUN_QUARANTINE, a space-separated list of environment variable names. Every variable found in MODULES_RUN_QUARANTINE will be set in quarantine during the modulecmd.tcl run-time. Their value will be set empty or set to the value of the corresponding MODULES_RUNENV_<VAR> environment variable if defined. Once modulecmd.tcl is started it restores quarantine variables to their original values.

MODULES_RUN_QUARANTINE and MODULES_RUNENV_<VAR> environment variables can be defined at build time by using the following configure option:

--with-quarantine-vars='VARNAME[=VALUE] ...'

Quarantine mechanism is available for all supported shells except csh and tcsh.

Pager support

The informational messages Modules sends on the stderr channel may sometimes be quite long. This is especially the case for the avail sub-command when hundreds of modulefiles are handled. To improve the readability of those messages, stderr output can now be piped into a paging command.

This new feature can be controlled at build time with the --with-pager and --with-pager-opts configure options. Default pager command is set to less and its relative options are by default -eFKRX. Default configuration can be supersedes at run-time with MODULES_PAGER environment variables or command-line switches (--no-pager, --paginate).

Warning

On version 4.1.0, the PAGER environment variable was taken in consideration to supersede pager configuration at run-time. Since version 4.1.1, PAGER environment variable is ignored to avoid side effects coming from the system general pager configuration.

Module function to return value in scripting languages

On Tcl, Perl, Python, Ruby, CMake and R scripting shells, module function was not returning value and until now an occurred error led to raising a fatal exception.

To make module function more friendly to use on these scripting shells it now returns a value. False in case of error, true if everything goes well.

As a consequence, returned value of a module sub-command can be checked. For instance in Python:

if module('load', 'foo'):
  # success
else:
  # failure

New modulefile commands

4 new modulefile Tcl commands have been introduced:

  • is-saved: returns true or false whether a collection, corresponding to currently set collection target, exists or not.
  • is-used: returns true or false whether a given directory is currently enabled in MODULEPATH.
  • is-avail: returns true or false whether a given modulefile exists in currently enabled module paths.
  • module-info loaded: returns the exact name of the modulefile currently loaded corresponding to the name argument.

Multiple collections, paths or modulefiles can be passed respectively to is-saved, is-used and is-avail in which case true is returned if at least one argument matches condition (acts as a OR boolean operation). No argument may be passed to is-loaded, is-saved and is-used commands to return if anything is respectively loaded, saved or used.

If no loaded modulefile matches the module-info loaded query, an empty string is returned.

New module sub-commands

Modulefile-specific commands are sometimes wished to be used outside of a modulefile context. Especially for the commands managing path variables or commands querying current environment context. So the following modulefile-specific commands have been made reachable as module sub-commands with same arguments and properties as if called from within a modulefile:

  • append-path
  • prepend-path
  • remove-path
  • is-loaded
  • info-loaded

The is-loaded sub-command returns a boolean value. Small Python example:

if module('is-loaded', 'app'):
  print 'app is loaded'
else:
  print 'app not loaded'

info-loaded returns a string value and is the sub-command counterpart of the module-info loaded modulefile command:

$ module load app/0.8
$ module info-loaded app
app/0.8

Further reading

To get a complete list of the changes between Modules v4.0 and v4.1, please read the Release notes document.

Migrating from v3.2 to v4.0

Major evolution occurs with this v4.0 release as the traditional module command implemented in C is replaced by the native Tcl version. This full Tcl rewrite of the Modules package was started in 2002 and has now reached maturity to take over the binary version. This flavor change enables to refine and push forward the module concept.

This document provides an outlook of what is changing when migrating from v3.2 to v4.0 by first describing the introduced new features. Both v3.2 and v4.0 are quite similar and transition to the new major version should be smooth. Slights differences may be noticed in a few use-cases. So the second part of the document will help to learn about them by listing the features that have been discontinued in this new major release or the features where a behavior change can be noticed.

New features

On its overall this major release brings a lot more robustness to the module command with now more than 4000 non-regression tests crafted to ensure correct operations over the time. This version 4.0 also comes with fair amount of improved functionalities. The major new features are described in this section.

Additional shells supported

Modules v4 introduces support for fish, lisp, tcl and R code output.

Non-zero exit code in case of error

All module sub-commands will now return a non-zero exit code in case of error whereas Modules v3.2 always returned zero exit code even if issue occurred.

Output redirect

Traditionally the module command output text that should be seen by the user on stderr since shell commands are output to stdout to change shell's environment. Now on sh, bash, ksh, zsh and fish shells, output text is redirected to stdout after shell command evaluation if shell is in interactive mode.

Filtering avail output

Results obtained from the avail sub-command can now be filtered to only get the default version of each module name with use of the --default or -d command line switch. Default version is either the explicitly set default version or the highest numerically sorted modulefile or module alias if no default version set.

It is also possible to filter results to only get the highest numerically sorted version of each module name with use of the --latest or -L command line switch.

Extended support for module alias and symbolic version

Module aliases are now included in the result of the avail, whatis and apropos sub-commands. They are displayed in the module path section where they are defined or in a global/user modulerc section for aliases set in user's or global modulerc file. A @ symbol is added in parenthesis next to their name to distinguish them from modulefiles.

Search may be performed with an alias or a symbolic version-name passed as argument on avail, whatis and apropos sub-commands.

Modules v4 resolves module alias or symbolic version passed to unload command to then remove the loaded modulefile pointed by the mentioned alias or symbolic version.

A symbolic version sets on a module alias is now propagated toward the resolution path to also apply to the relative modulefile if it still correspond to the same module name.

Hiding modulefiles

Visibility of modulefiles can be adapted by use of file mode bits or file ownership. If a modulefile should only be used by a given subset of persons, its mode an ownership can be tailored to provide read rights to this group of people only. In this situation, module only reports the modulefile, during an avail command for instance, if this modulefile can be read by the current user.

These hidden modulefiles are simply ignored when walking through the modulepath content. Access issues (permission denied) occur only when trying to access directly a hidden modulefile or when accessing a symbol or an alias targeting a hidden modulefile.

Improved modulefiles location

When looking for an implicit default in a modulefile directory, aliases are now taken into account in addition to modulefiles and directories to determine the highest numerically sorted element.

Modules v4 resolves module alias or symbolic version when it points to a modulefile located in another modulepath.

Access issues (permission denied) are now distinguished from find issues (cannot locate) when trying to access directly a directory or a modulefile as done on load, display or whatis commands. In addition, on this kind of access not readable .modulerc or .version files are ignored rather producing a missing magic cookie error.

Module collection

Modules v4 introduces support for module collections. Collections describe a sequence of module use then module load commands that are interpreted by Modules to set the user environment as described by this sequence. When a collection is activated, with the restore sub-command, modulepaths and loaded modules are unused or unloaded if they are not part or if they are not ordered the same way as in the collection.

Collections are generated by the save sub-command that dumps the current user environment state in terms of modulepaths and loaded modules. By default collections are saved under the $HOME/.module directory. Collections can be listed with savelist sub-command, displayed with saveshow and removed with saverm.

Collections may be valid for a given target if they are suffixed. In this case these collections can only be restored if their suffix correspond to the current value of the MODULES_COLLECTION_TARGET environment variable. Saving collection registers the target footprint by suffixing the collection filename with .$MODULES_COLLECTION_TARGET.

Path variable element counter

Modules 4 provides path element counting feature which increases a reference counter each time a given path entry is added to a given path-like environment variable. As consequence a path entry element is removed from a path-like variable only if the related element counter is equal to 1. If this counter is greater than 1, path element is kept in variable and reference counter is decreased by 1.

This feature allows shared usage of particular path elements. For instance, modulefiles can append /usr/local/bin to PATH, which is not unloaded until all the modulefiles that loaded it unload too.

Optimized I/O operations

Substantial work has been done to reduce the number of I/O operations done during global modulefile analysis commands like avail or whatis. stat, open, read and close I/O operations have been cut down to the minimum required when walking through the modulepath directories to check if files are modulefiles or to resolve module aliases.

Interpretation of modulefiles and modulerc are handled by the minimum required Tcl interpreters. Which means a configured Tcl interpreter is reused as much as possible between each modulefile interpretation or between each modulerc interpretation.

Sourcing modulefiles

Modules 4 introduces the possibility to source a modulefile rather loading it. When it is sourced, a modulefile is interpreted into the shell environment but then it is not marked loaded in shell environment which differ from load sub-command.

This functionality is used in shell initialization scripts once module function is defined. There the etc/modulerc modulefile is sourced to setup the initial state of the environment, composed of module use and module load commands.

Removed features and substantial behavior changes

Following sections provide list of Modules v3.2 features that are discontinued on Modules v4 or features with a substantial behavior change that should be taken in consideration when migrating to v4.

Package initialization

MODULESBEGINENV environment snapshot functionality is not supported anymore on Modules v4. Modules collection mechanism should be used instead to save and restore sets of enabled modulepaths and loaded modulefiles.

Command line switches

Some command line switches are not supported anymore on v4.0. When still using them, a warning message is displayed and the command is ran with these unsupported switches ignored. Following command line switches are concerned:

  • --force, -f
  • --human
  • --verbose, -v
  • --silent, -s
  • --create, -c
  • --icase, -i
  • --userlvl lvl, -u lvl

Module sub-commands

During an help sub-command, Modules v4 does not redirect output made on stdout in ModulesHelp Tcl procedure to stderr. Moreover when running help, version 4 interprets all the content of the modulefile, then call the ModulesHelp procedure if it exists, whereas Modules 3.2 only interprets the ModulesHelp procedure and not the rest of the modulefile content.

When load is asked on an already loaded modulefiles, Modules v4 ignores this new load order whereas v3.2 refreshed shell alias definitions found in this modulefile.

When switching on version 4 an old modulefile by a new one, no error is raised if old modulefile is not currently loaded. In this situation v3.2 threw an error and abort switch action. Additionally on switch sub-command, new modulefile does not keep the position held by old modulefile in loaded modules list on Modules v4 as it was the case on v3.2. Same goes for path-like environment variables: replaced path component is appended to the end or prepended to the beginning of the relative path-like variable, not appended or prepended relatively to the position hold by the swapped path component.

During a switch command, version 4 interprets the swapped-out modulefile in unload mode, so the sub-modulefiles loaded, with module load order in the swapped-out modulefile are also unloaded during the switch.

Modules 4 provides path element counting feature which increases a reference counter each time a given path entry is added to a given environment variable. This feature also applies to the MODULEPATH environment variable. As consequence a modulepath entry element is removed from the modulepath enabled list only if the related element counter is equal to 1. When unusing a modulepath if its reference counter is greater than 1, modulepath is kept enabled and reference counter is decreased by 1.

On Modules 3.2 paths composing the MODULEPATH environment variable may contain reference to environment variable. These variable references are resolved dynamically when MODULEPATH is looked at during module sub-command action. This feature has been discontinued on Modules v4.

Following Modules sub-commands are not supported anymore on v4.0:

  • clear
  • update

Modules specific Tcl commands

Modules v4 provides path element counting feature which increases a reference counter each time a given path entry is added to a given environment variable. As a consequence a path entry element is not always removed from a path-like variable when calling to remove-path or calling to append-path or append-path at unloading time. The path element is removed only if its related element counter is equal to 1. If this counter is greater than 1, path element is kept in variable and reference counter is decreased by 1.

On Modules v4, module-info mode returns during an unload sub-command the unload value instead of remove on Modules v3.2. However if mode is tested against remove value, true will be returned. During a switch sub-command on Modules v4, unload then load is returned instead of switch1 then switch2 then switch3 on Modules v3.2. However if mode is tested against switch value, true will be returned.

When using set-alias, Modules v3.2 defines a shell function when variables are in use in alias value on Bourne shell derivatives, Modules 4 always defines a shell alias never a shell function.

Some Modules specific Tcl commands are not supported anymore on v4.0. When still using them, a warning message is displayed and these unsupported Tcl commands are ignored. Following Modules specific Tcl commands are concerned:

  • module-info flags
  • module-info trace
  • module-info tracepat
  • module-info user
  • module-log
  • module-trace
  • module-user
  • module-verbosity

Further reading

To get a complete list of the differences between Modules v3.2 and v4, please read the Differences between versions 3.2 and 4 document.

A significant number of issues reported for v3.2 have been closed on v4. List of these closed issues can be found at:

https://github.com/cea-hpc/modules/milestone/1?closed=1