Creating module files

A complex program in Linux will generally be installed in multiple locations. For example, a C++ library like Magick++ after installation will require include files, library files and binary files. Each of these is located in different folders and may be in different parent directories aw well.

In one of our installation, Magick++ is installed in /usr/local/magick++/magick++/. Under this directory, the include files are in include, the library files are in lib and binary files are in bin.

For a user defined program using the Magick++ library, the path to all three have to be in their environment variable. This is set using a module file.

A module file is a TCL script. An example of the module file for adding path to magick++ is given below.


#%Module######################################################################
##
## Magick++ Module
##
proc ModulesHelp { } {
puts stderr "\tThis module adds PATH that allow you to compile Magick++
}

set MAGICK_LIB_HOME "/usr/local/magick++/magick++/lib"
set MAGICK_BIN_HOME "/usr/local/magick++/magick++/bin"
set MAGICK_INCLUDE_HOME "/usr/local/magick++/magick++/include"

append-path PATH $MAGICK_BIN_HOME
append-path LD_LIBRARY_PATH $MAGICK_LIB_HOME
append-path LD_INCLUDE_PATH $MAGICK_INCLUDE_HOME


The module file begins with #%Module, which helps to identify a module file. The proc ModulesHelp prints a helpful message whenever "module help magick++" is typed in linux command prompt. The next three lines create variables that store the location of lib, bin and include direcory. Finally these paths are appended to the environment variables PATH, LD_LIBRARY_PATH and LD_INCLUDE_PATH respectively.

To invoke this module file and attach all these path to environment variables, type "module load magick++" or "module add magick++" at the Linux command line.

To unload these path and environment variables, type "module unload magick++"

In addition to appending path, we can also prepend paths, set and unset environment variables, set and unset aliases etc. Refer to the manpage for more details.