CLASSPATH problems

Having problems getting Weka to run from a DOS/UNIX command prompt? Getting java.lang.NoClassDefFoundError exceptions? Most likely your CLASSPATH environment variable is not set correctly - it needs to point to the weka.jar file that you downloaded with Weka (or the parent of the Weka directory if you have extracted the jar). Under DOS this can be achieved with:
 set CLASSPATH=c:\weka-3-4\weka.jar;%CLASSPATH%
Under UNIX/Linux something like:
 export CLASSPATH=/home/weka/weka.jar:$CLASSPATH
An easy way to get avoid setting the variable this is to specify the CLASSPATH when calling Java. For example, if the jar file is located at c:\weka-3-4\weka.jar you can use:
 java -cp c:\weka-3-4\weka.jar weka.classifiers... 
See also the CLASSPATH article.