modulefile (4) - Linux Manuals

modulefile: files containing Tcl code for the Modules package


modulefile - files containing Tcl code for the Modules package


modulefiles are written in the Tool Command Language, Tcl(3) and are interpreted by the modulecmd 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 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.

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 modulefile 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(3) 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.

The integer value N after the exit command will be used as an command exit value; however, some shells (bash being one of them) do not carry this value through an eval though. For bash and those Bourne shells (/bin/sh) being emulated by the bash will have return a non-zero value as a result of test 0 = 1 being appended to the evaluate string.

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 [ modulefile ... ]
conflict modulefile [ 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 [ 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 remove 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 program's state. Some of the information is specific to the internals of modulecmd. 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 flags
Returns the integer value of modulecmd's flags state.
module-info mode [modetype]
Returns the current modulecmd's mode as a string if no modetype is given.

Returns 1 if modulecmd's mode is modetype. modetype can be: load, remove, display, help, whatis, switch, switch1, switch2, or switch3.

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
Return the current shell under which modulecmd was invoked. This is the first parameter of modulecmd, which is normally hidden by the module alias.
module-info shelltype
Return the family of the shell under which modulefile was invoked. As of module-info shell this depends on the first parameter of modulecmd. The output reflects a shell type determining the shell syntax of the commands produced by modulecmd.
module-info alias name
Returns the full module file name to which the module file alias name is assigned
module-info version module-file
Returns a list of all symbolic versions assigned to the passed module-file. The paremeter module-file might either be a full qualified module file with name and version, another symbolic module file name or a module file alias.

module-version module-file version-name [version-name ...]

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

The parameter module-file may be either

a fully qualified modulefile with name and version
a symbolic module file name
another module file alias

module-alias name module-file

Assignes the module file module-file to the alias name. This command should be placed in one of the modulecmd rc files in order to provide shorthand invocations of frequently used module file names.

The parameter module-file may be either

a fully qualified modulefile with name and version
a symbolic module file name
another module file alias

module-trace {on|off} [command [command ...]] [-module modulefile [modulefile ...]]

Switches tracing on or off. Without parameters this command will affect globally all tracing setups for all commands and modulefiles. The command parameter may be used to affect tracing of specified module commands only and the switch -module finally limits the affect of the module-trace command to a well defined set of module files.

The command may be one of the following

avail - 'module avail' command
clear - 'module clear' command
display - 'module display' command
init - 'module init' command
help - 'module help' command
list - 'module list' command
load - 'module load' command
purge - 'module purge' command
switch - 'module switch' command
unuse - 'module unuse' command
unload - 'module unload' command
update - 'module update' command
use - 'module use' command

The module parameter specifies a set of module files using TCL regular expressions. For example

.* will affect all module files
*/2.0 affects all module files at version 2.0
gnu/.* affects all versions of the gnu modulefile
gnu/2.0 affects only version 2.0 of the gnu modulefile

The module parameter is prepended to the current tracing pattern list for the specified module command. It is evaluated from the left to the right. The first matching pattern defines the tracing parameter.

The internal trace pattern list is stored as a colon separated list. In advanced user level only, colons may be specified on the module parameter of the module-trace command. This will directly take effect in the internal trace pattern list. In novice or expert user level a warning messge will be generated.

module-user level

Defines the user level under wich module-cmd runs. This takes effect on the error messages being produced and on the behavior of modulecmd in case of detecting an outage.

The level parameter specifies the user level and may be one of the following values:

advanced, adv - advanced user level
expert, exp - expert user level
novice, nov - novice user level

module-verbosity {on|off}

Switches verbose modulecmd message display on or off.

module-log error-weight log-facility

Defines whether error messages of the specified weight should be logged and conditionally assignes a log-facility.

The error-weight parameter specifies the error level to be logged. It may be one of the following values:

verb - verbose messages
info - informal messages
debug - debugging messages
trace - tracing output
warn - warnings
prob - problems (normally the modulecmd may be completed)
error - errors (which normally leads to unsuccessful end of the modulecmd)
fatal - fatal system errors
panic - very fatal system errors, e.g. internal program inconsistencies.

The log-facility parameter specifies the log destination. This may either switch off logging for the specified error-weight, direct log messages to a special stream or a file or specify a syslog facility for logging. The following values are allowed:

stderr, stdout - predefined output streams for normal and error outputs. Note, that stdout is normally used for passing parameters to the invoking shell. Directing error output to this stream might screw up the modulecmd integration to your shell.
a syslog facility - directs logging to the syslog. See syslog.conf(4) for detailed description of the valid syslog facilities.
null, none - will suppress logging of the specified error-weight.
a filename - is recognized by the first character being either a '.' or a '/'. You must have write permission to the file you specify.

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.

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. Arguments can be specified using the Bourne Shell style of function arguments. If the string contains "$1", then this will become the first argument when the alias is interpreted by the shell. The string "$*" corresponds to all of the arguments given to the alias. The character '$' may be escaped using the '\' character.

For some shells, aliases are not possible and the command has no effect. For Bourne shell derivatives, a shell function will be written (if supported) to give the impression of an alias. 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. If the shell supports functions then the shell is instructed to unset function alias-name.

system string

Pass string to the C library routine system(3). For the system(3) call modulecmd 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 fast lookup of system information on systems that support uname(3). uname is significantly faster than using system to execute a program to return host information. If uname(3) is not available, gethostname(3) or some program will make the nodename available. uname will return the string "unknown" if information is unavailable for the field.

uname will invoke getdomainname in order 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
x-resource 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. If a file is found, it will be filtered through the cpp(1) preprocessor, just as xrdb(1) would do.

modulefiles that use this command, should in most cases contain one or more x-resource lines, each defining one X11 resource. Reading resources from filename is much slower, due to the preprocessing. 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 file Ileaf is preprocessed by cpp(1) and the result 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 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 module file 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 module file 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 will use the name as if it specifies a modulefile in the directory. This will become the default module file 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. So, changes made in these file will affect the subsequently interpreted modulefile.

If no default version may be figured out, then the highest lexicographically sorted modulefile under the directory using the 'C' locale will be used.

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"

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 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 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.




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

TclX was developed by Karl Lehenbauer and Mark Diekhans.


module(1), Tcl(3), TclX(3), xrdb(1), cpp(1), system(3), uname(3), gethostname(3) getdomainname(3)