This cmd works using shell command on Linux and XShell on Windows, but not XShell on Linux.
$JYTHON/xyz.py --showConfig

This is the value of JYTHON:
JYTHON=$JAVA -jar $JYTHON_JAR -Dpython.path=$PYTHON_LOC $PYTHON_LOC

Using the individual variables works using XShell on Linux:
$JAVA -jar $JYTHON_JAR -Dpython.path=$PYTHON_LOC $PYTHON_LOC/xyz.py --showConfig

I think the reason for this is that linux treats each variable as a single argument. This is the reason Ant has <arg line> vs <arg value> support to distinguish handling of spaces within args on linux. (See: https://ant.apache.org/manual/using.html#arg)