Ubuntu should have gdb for debugging.
Or you can output the information for a simple problem you can check by hand to see if the results are correct.
Feap has a matrix output routine for real quantities:
For example if you have:
real*8 aa(nd,nc)
you can output part of the array using
call mprint(aa,nrow,ncol,nd,'AA')
A similar routine exists for integer (integer*4) as call iprint(ia,nrow,ncol,nd,'IA')
In the above 'ND' is the first dimension, 'NROW','NCOL' the amount you would like to output.
EXAMPLE
real*8 c(6,7)
call mprint(c,6,7,6,'C")
would output the entire array.