afni.nimh.nih.gov

The dry_run option is useful for creating your own script. It doesn't actually read the dataset, so the 1.234567 is just a filler for an actual value for the spacing. The e2a matrix is a temporary matrix that corresponds to just the alignment between anat and epi and does not include obliquity, motion correction or an alignment transformation to a standard template. It is saved as "e2a" because 3dAllineate saves the matrix in terms of a base to source transformation instead of the direction you might expect, source to base - anat to epi.