Hello Krik, 

It worked through the terminal!

One more thing I would like to ask you about is that how we view the colored map?
in FSL, vector files are usually generated for DTI maps and we use them to view FA colored map for example. 

Someone suggested ImageJ, but still DKE gives only maps and doesnt give the principle vectors. So how can we view the colored maps?

Thanks, 
Wafaa