== Software Environment with Module ==


<<TableOfContents>>

=== Overview ===
 More and more software at DESY is configured through the use of the module command. This allows loading and unloading different software packages (modules) on the fly, automatically making all of the necessary changes to your shell environment (variables for library and binary search paths, etc.). For example, you can choose between different versions of the same software package, or between different builds of the same library compiled with different compilers, etc.

=== Caveats ===
Extending $PATH and $LD_LIBRARY_PATH to locations on non-local storage can have adverse effects on your user experience (delays, hangs). It is therefore not recommended to execute module commands in your dot files. Instead, they should only be used in the shell instance where they are actually required.

=== Commands ===

||<rowbgcolor="#ffffe0"> Command || Comments ||
|| module --help   || ||
|| module avail    || to list all available modules you can load ||
|| module list     || to list your currently loaded modules ||
|| module load ''moduleName''  || to load ''moduleName'' into your environment ||
|| module unload ''moduleName'' || to unload ''moduleName'' from your environment ||
|| module switch ''oldmoduleName newmoduleName'' ||first unloads module ''oldmoduleName'' then loads module ''newmoduleName'' ||
|| module display ''moduleName'' || lists the environment variables set up by the module ''moduleName'' ||
|| module whatis ''moduleName''  || more information about the software package ''moduleName'' ||
|| module whatis || list of available modules, with brief description ||


=== Examples ===
 * on SL6 available:
{{{
module avail
------------------------------------- /usr/share/Modules/modulefiles -------------------------------------
dot         module-cvs  module-info modules     null        use.own

-------------------------------------------- /etc/modulefiles --------------------------------------------
intel.2011           maple.15             matlab/R2012a        openmpi-x86_64       texlive/2011
maple/16             math.7               matlab.R2011a        openmpi-x86_64-intel texlive/2012
maple.14             math.8               openmpi-i386         pgi.2011

}}}

 * on SL6 available maple versions
{{{
module avail maple/
-------------------------------------------- /etc/modulefiles --------------------------------------------
maple/16 maple.14 maple.15
}}}
 * load maple, list the loaded packages and show information about maple
{{{
module load maple
}}}
{{{
module list         
Currently Loaded Modulefiles:
  1) maple/16
}}}
{{{
module display maple
-------------------------------------------------------------------
/etc/modulefiles/maple/16:

module-whatis	 Setup Maple version 16  
prepend-path	 PATH /opt/maple/16/bin 
-------------------------------------------------------------------
}}}

=== module vs. ini ===
Environment modules are replacing `ini`. The former are widely used in scientific computing, while `ini` is practically unheard of outside DESY even though it's not necessarily inferior. There is a rough correspondence between `ini` and `module` commands:

||<rowbgcolor="#ffffe0"> ini command || module command || purpose ||
|| ini || module whatis || list available modules, with brief description ||
|| ini || module avail    || list all available modules you can load ||
|| ini || module list      || list your currently loaded modules ||
|| ini ''something'' || module load ''something''  || load ''something'' into your environment ||
|| ini ''-something'' || module unload ''something'' || unload ''something'' from your environment ||
|| - || module switch ''oldmoduleName newmoduleName'' ||first unloads module ''oldmoduleName'' then loads module ''newmoduleName'' ||
|| - || module display ''moduleName'' || lists the environment variables set up by the module ''moduleName'' ||




=== Remarks ===
 * At the beginning of using modules, we hadn't pushed a whatis file, which makes the output of `module whatis` incomplete. This is being corrected as we roll out updated software packages.
 * The different versions of a product have to follow the naming convention ''<product>/<version>''. This, too,  is being corrected as we roll out updated software packages.
 * If there are several versions of a module, the latest (in lexical order) is used automatically unless specified otherwise.