MODULEFILE(4) manual page (Tcl version)

modulefile - files containing Tcl code for the Modules package


modulefiles are written in the Tool Command Language, Tcl(n) and are interpreted by the modulecmd.tcl program via the module(1) user interface. modulefiles can be loaded, unloaded, or switched on-the-fly while the user is working; and can be used to implement site policies regarding the access and use of applications.

A modulefile begins with the magic cookie, '#%Module'. A version number may be placed after this string. The version number is useful as the modulefile format may change. If a version number doesn't exist, then modulecmd.tcl will assume the modulefile is compatible with the latest version. The current modulefile version is 1.0. Files without the magic cookie will not be interpreted by modulecmd.tcl.

Each modulefile contains the changes to a user's environment needed to access an application. Tcl is a simple programming language which permits modulefiles to be arbitrarily complex, depending upon the application's and the modulefile writer's needs. If support for extended tcl (tclX) has been configured for your installation of the Modules package, you may use all the extended commands provided by tclX, too.

A typical modulefiles is a simple bit of code that set or add entries to the PATH, MANPATH, or other environment variables. Tcl has conditional statements that are evaluated when the modulefile is loaded. This is very effective for managing path or environment changes due to different OS releases or architectures. The user environment information is encapsulated into a single modulefile kept in a central location. The same modulefile is used by every user on any machine. So, from the user's perspective, starting an application is exactly the same irrespective of the machine or platform they are on.

modulefiles also hide the notion of different types of shells. From the user's perspective, changing the environment for one shell looks exactly the same as changing the environment for another shell. This is useful for new or novice users and eliminates the need for statements such as "if you're using the C Shell do this ..., otherwise if you're using the Bourne shell do this ...". Announcing and accessing new software is uniform and independent of the user's shell. From the modulefile writer's perspective, this means one set of information will take care of every type of shell.

Modules Specific Tcl Commands

The Modules Package uses commands which are extensions to the "standard" Tool Command Language Tcl(n) package. Unless otherwise specified, the Module commands return the empty string. Some commands behave differently when a modulefile is loaded or unloaded. The command descriptions assume the modulefile is being loaded.


This is not a Modules-specific command, it's actually part of Tcl, which has been overloaded similar to the continue and exit commands to have the effect of causing the module not to be listed as loaded and not affect other modules being loaded concurrently. All non-environment commands within the module will be performed up to this point and processing will continue on to the next module on the command line. The break command will only have this effect if not used within a Tcl loop though.

An example: Suppose that a full selection of modulefiles are needed for various different architectures, but some of the modulefiles are not needed and the user should be alerted. Having the unnecessary modulefile be a link to the following notavail modulefile will perform the task as required.

    ## notavail modulefile
    proc ModulesHelp { } {
        puts stderr "This module does nothing but alert the user"
        puts stderr "that the [module-info name] module is not available"

    module-whatis "Notifies user that module is not available."
    set curMod [module-info name]
    if { [ module-info mode load ] } {
        puts stderr "Note: '$curMod' is not available for [uname sysname]."
chdir directory

Set the current working directory to directory.


This is not a modules specific command but another overloaded Tcl command and is similar to the break or exit commands except the module will be listed as loaded as well as performing any environment or Tcl commands up to this point and then continuing on to the next module on the command line. The continue command will only have this effect if not used within a Tcl loop though.

exit [N]

This is not a modules specific command but another overloaded Tcl command and is similar to the break or continue commands. However, this command will cause the immediate cessation of this module and any additional ones on the command line. This module and the subsequent modules will not be listed as loaded. No environment commands will be performed in the current module.

setenv variable value

Set environment variable to value. The setenv command will also change the process' environment. A reference using Tcl's env associative array will reference changes made with the setenv command. Changes made using Tcl's env associative array will NOT change the user's environment variable like the setenv command. An environment change made this way will only affect the module parsing process. The setenv command is also useful for changing the environment prior to the exec or system command. When a modulefile is unloaded, setenv becomes unsetenv. If the environment variable had been defined it will be overwritten while loading the modulefile. A subsequent unload will unset the environment variable - the previous value cannot be restored! (Unless you handle it explicitly ... see below.)

unsetenv variable [value]

Unsets environment variable. However, if there is an optional value, then when unloading a module, it will set variable to value. The unsetenv command changes the process' environment like setenv.

append-path [-d C|--delim C|--delim=C] variable value
prepend-path [-d C|--delim C|--delim=C] variable value

Append or prepend value to environment variable. The variable is a colon, or delimiter, separated list such as PATH=directory:directory:directory. The default delimiter is a colon ':', but an arbitrary one can be given by the --delim option. For example a space can be used instead (which will need to be handled in the Tcl specially by enclosing it in " " or { }). A space, however, can not be specified by the --delim=C form.

If the variable is not set, it is created. When a modulefile is unloaded, append-path and prepend-path become remove-path.

remove-path [-d C|--delim C|--delim=C] variable value

Remove value from the colon, or delimiter, separated list in variable. See prepend-path or append-path for further explanation of using an arbitrary delimiter. Every string between colons, or delimiters, in variable is compared to value. If the two match, value is removed from variable.

prereq modulefile...
conflict modulefile...

prereq and conflict control whether or not the modulefile will be loaded. The prereq command lists modulefiles which must have been previously loaded before the current modulefile will be loaded. Similarly, the conflict command lists modulefiles which conflict with the current modulefile. If a list contains more than one modulefile, then each member of the list acts as a Boolean OR operation. Multiple prereq and conflict commands may be used to create a Boolean AND operation. If one of the requirements have not been satisfied, an error is reported and the current modulefile makes no changes to the user's environment.

If an argument for prereq is a directory and any modulefile from the directory has been loaded, then the prerequisite is met. For example, specifying X11 as a prereq means that any version of X11, X11/R4 or X11/R5, must be loaded before proceeding.

If an argument for conflict is a directory and any other modulefile from that directory has been loaded, then a conflict will occur. For example, specifying X11 as a conflict will stop X11/R4 and X11/R5 from being loaded at the same time.

is-loaded modulefile...

The is-loaded command returns a true value if any of the listed modulefiles has been loaded. If a list contains more than one modulefile, then each member acts as a boolean OR operation. If an argument for is-loaded is a directory and any modulefile from the directory has been loaded is-loaded would return a true value.

module [sub-command] [sub-command-args]

Contains the same sub-commands as described in the module(1) man page in the Module Sub-Commands section. This command permits a modulefile to load or unload other modulefiles. No checks are made to ensure that the modulefile does not try to load itself. Often it is useful to have a single modulefile that performs a number of module load commands. For example, if every user on the system requires a basic set of applications loaded, then a core modulefile would contain the necessary module load commands.

module-info option [info-args]

Provide information about the modulecmd.tcl program's state. Some of the information is specific to the internals of modulecmd.tcl. option is the type of information to be provided, and info-args are any arguments needed.

module-info type

Returns either "C" or "Tcl" to indicate which module command is being executed, either the "C" version or the Tcl-only version, to allow the modulefile writer to handle any differences between the two.

module-info mode [modetype]

Returns the current modulecmd.tcl's mode as a string if no modetype is given.

Returns 1 if modulecmd.tcl's mode is modetype. modetype can be: load, unload, remove, switch, display, help, test or whatis.

module-info command [commandname]

Returns the currently running modulecmd.tcl's command as a string if no commandname is given.

Returns 1 if modulecmd.tcl's command is commandname. commandname can be: load, unload, reload, source, switch, display, avail, aliases, list, whatis, search, purge, restore, help or test.

module-info name

Return the name of the modulefile. This is not the full pathname for modulefile. See the Modules Variables section for information on the full pathname.

module-info specified

Return the name of the modulefile specified on the command line.

module-info shell [shellname]

Return the current shell under which modulecmd.tcl was invoked if no shellname is given. The current shell is the first parameter of modulecmd.tcl, which is normally hidden by the module alias.

If a shellname is given, returns 1 if modulecmd.tcl's current shell is shellname, returns 0 elsewhere. shellname can be: sh, bash, ksh, zsh, csh, tcsh, fish, tcl, perl, python, ruby, lisp, cmake, r.

module-info shelltype [shelltypename]

Return the family of the shell under which modulefile was invoked if no shelltypename is given. As of module-info shell this depends on the first parameter of modulecmd.tcl. The output reflects a shell type determining the shell syntax of the commands produced by modulecmd.tcl.

If a shelltypename is given, returns 1 if modulecmd.tcl's current shell type is shelltypename, returns 0 elsewhere. shelltypename can be: sh, csh, fish, tcl, perl, python, ruby, lisp, cmake, r.

module-info alias name

Returns the full modulefile name to which the modulefile alias name is assigned

module-info version modulefile

Returns the physical module name and version of the passed symbolic version modulefile. The parameter modulefile might either be a full qualified modulefile with name and version, another symbolic modulefile name or a modulefile alias.

module-info symbols modulefile

Returns a list of all symbolic versions assigned to the passed modulefile. The parameter modulefile might either be a full qualified modulefile with name and version, another symbolic modulefile name or a modulefile alias.

module-version modulefile version-name...

Assigns the symbolic version-name to the modulefile. This command should be placed in one of the modulecmd.tcl rc files in order to provide shorthand invocations of frequently used modulefile names.

The special version-name default specifies the default version to be used for module commands, if no specific version is given. This replaces the definitions made in the .version file in former modulecmd.tcl releases.

The parameter modulefile may be either

  • a fully or partially qualified modulefile with name / version. If name is '.' then the current directory name is assumed to be the module name. (Use this for deep modulefile directories.)

  • a symbolic modulefile name

  • another modulefile alias

module-alias name modulefile

Assigns the modulefile to the alias name. This command should be placed in one of the modulecmd.tcl rc files in order to provide shorthand invocations of frequently used modulefile names.

The parameter modulefile may be either

  • a fully qualified modulefile with name and version

  • a symbolic modulefile name

  • another modulefile alias

module-whatis string

Defines a string which is displayed in case of the invocation of the module whatis command. There may be more than one module-whatis line in a modulefile. This command takes no actions in case of load, display, etc. invocations of modulecmd.tcl.

The string parameter has to be enclosed in double-quotes if there's more than one word specified. Words are defined to be separated by whitespace characters (space, tab, cr).

set-alias alias-name alias-string

Sets an alias or function with the name alias-name in the user's environment to the string alias-string. For some shells, aliases are not possible and the command has no effect. When a modulefile is unloaded, set-alias becomes unset-alias.

unset-alias alias-name

Unsets an alias with the name alias-name in the user's environment.

system string

Pass string to the Tcl built-in command exec(n). For the exec(n) call modulecmd.tcl redirects stdout to stderr since stdout would be parsed by the evaluating shell. The exit status of the executed command is returned.

uname field

Provide lookup of system information. Most field information are retrieved from the tcl_platform array (see tclvars(n) man page). Uname will return the string "unknown" if information is unavailable for the field.

uname will invoke uname(1) command in order to get the operating system version and domainname(1) to figure out the name of the domain.

field values are:

  • sysname: the operating system name

  • nodename: the hostname

  • domain: the name of the domain

  • release: the operating system release

  • version: the operating system version

  • machine: a standard name that identifies the system's hardware

x-resource [resource-string|filename]

Merge resources into the X11 resource database. The resources are used to control look and behavior of X11 applications. The command will attempt to read resources from filename. If the argument isn't a valid file name, then string will be interpreted as a resource. Either filename or resource-string is then passed down to be xrdb(1) command.

modulefiles that use this command, should in most cases contain one or more x-resource lines, each defining one X11 resource. The DISPLAY environment variable should be properly set and the X11 server should be accessible. If x-resource can't manipulate the X11 resource database, the modulefile will exit with an error message.


x-resource /u2/staff/leif/.xres/Ileaf

The content of the Ileaf file is merged into the X11 resource database.

x-resource [glob ~/.xres/ileaf]

The Tcl glob function is used to have the modulefile read different resource files for different users.

x-resource {Ileaf.popup.saveUnder: True}

Merge the Ileaf resource into the X11 resource database.

Modules Variables

The ModulesCurrentModulefile variable contains the full pathname of the modulefile being interpreted.

Locating Modulefiles

Every directory in MODULEPATH is searched to find the modulefile. A directory in MODULEPATH can have an arbitrary number of sub-directories. If the user names a modulefile to be loaded which is actually a directory, the directory is opened and a search begins for an actual modulefile. First, modulecmd.tcl looks for a file with the name .modulerc in the directory. If this file exists, its contents will be evaluated as if it was a modulefile to be loaded. You may place module-version and module-alias commands inside this file.

Additionally, before seeking for .modulerc files in the module directory, the global modulerc file is sourced, too. If a named version default now exists for the modulefile to be loaded, the assigned modulefile now will be sourced. Otherwise the file .version is looked up in the directory.

If the .version file exists, it is opened and interpreted as Tcl code and takes precedence over a .modulerc file in the same directory. If the Tcl variable ModulesVersion is set by the .version file, modulecmd.tcl will use the name as if it specifies a modulefile in the directory. This will become the default modulefile in this case.

If ModulesVersion is a directory, the search begins anew down that directory. If the name does not match any files located in the current directory, the search continues through the remaining directories in MODULEPATH.

Every .version and .modulerc file found is Tcl interpreted. The difference is that .version only applies to the current directory, and the .modulerc applies to the current directory and all subdirectories. Changes made in these files will affect the subsequently interpreted modulefile.

If no default version may be figured out, then the highest numerically sorted modulefile or module alias under the directory will be used. The dictionary comparison method of the lsort(n) Tcl command is used to achieve this sort. If highest numerically sorted element is an alias, search continues on its modulefile target.

For example, it is possible for a user to have a directory named X11 which simply contains a .version file specifying which version of X11 is to be loaded. Such a file would look like:

    ##  The desired version of X11
    set ModulesVersion "R4"

The equivalent .modulerc would look like:

    ##  The desired version of X11
    module-version "./R4" default

If user names a modulefile that cannot be found in the first modulepath directory, modulefile will be searched in next modulepath directory and so on until a matching modulefile is found. If search goes through a module alias or a symbolic version, this alias or symbol is resolved by first looking at the modulefiles in the modulepath where this alias or symbol is defined. If not found, resolution looks at the other modulepaths in their definition order.

When locating modulefiles, if a .modulerc, a .version, a directory or a modulefile cannot be read during the search it is simply ignored with no error message produced. Visibility of modulefiles can thus be adapted to the rights the user has been granted. Exception is made when trying to directly access a directory or a modulefile. In this case, the access issue is returned as an error message.

A modulefile whose name or element in its name starts with a '.' dot is considered hidden. Hidden modulefile is not displayed or taken into account except if it is explicitly named. By inheritance, a symbolic version-name assigned to a hidden modulefile is displayed or taken into account only if explicitly named. Module alias targeting a hidden modulefile appears like any other module alias.

Modulefile Specific Help

Users can request help about a specific modulefile through the module(1) command. The modulefile can print helpful information or start help oriented programs by defining a ModulesHelp subroutine. The subroutine will be called when the module help modulefile command is used.

Modulefile Specific Test

Users can request test of a specific modulefile through the module(1) command. The modulefile can perform some sanity checks on its definition or on its underlying programs by defining a ModulesTest subroutine. The subroutine will be called when the module test modulefile command is used. The subroutine should return 1 in case of success. If no or any other value is returned, test is considered failed.

Modulefile Display

The module display modulefile command will detail all changes that will be made to the environment. After displaying all of the environment changes modulecmd.tcl will call the ModulesDisplay subroutine. The ModulesDisplay subroutine is a good place to put additional descriptive information about the modulefile.



Path of directories containing modulefiles.


module(1), Tcl(n), TclX(n), xrdb(1), exec(n), uname(1), domainname(1), tclvars(n), lsort(n)


Tcl was developed by John Ousterhout at the University of California at Berkeley.

TclX was developed by Karl Lehenbauer and Mark Diekhans.