Are you sure you are using the correct java version? It looks like the option -jar is not known to your java version.
Have you tried:
java -version
or
which java
You can also try this:
java -cp <list all *.jar files> phex.Main
For reference see:
http://java.sun.com/j2se/1.4.2/docs/...inux/java.html http://java.sun.com/j2se/1.4.2/docs/...classpath.html