mahout command seq2sparse

when run the command like:

mahout seq2sparse -i inputfile -o outputfile

where is the command seq2sparse defined? how does the system know to
actually run the SparseFileFromSequenceFile class?

what is the language used in the command Mahout such as the language given
below:

========================================

THIS="$0"
while [ -h "$THIS" ]; do
ls=`ls -ld "$THIS"`
link=`expr "$ls" : '.*-> \(.*\)$'`
if expr "$link" : '.*/.*' > /dev/null; then
THIS="$link"
else
THIS=`dirname "$THIS"`/"$link"
fi
done

IS_CORE=0
if [ "$1" == "-core" ] ; then
IS_CORE=1
shift
fi

if [ "$MAHOUT_CORE" != "" ]; then
IS_CORE=1
fi

# some directories
THIS_DIR=`dirname "$THIS"`
MAHOUT_HOME=`cd "$THIS_DIR/.." ; pwd`

# some Java parameters
if [ "$MAHOUT_JAVA_HOME" != "" ]; then
#echo "run java in $MAHOUT_JAVA_HOME"
JAVA_HOME=$MAHOUT_JAVA_HOME
fi