to help you process your file you may find the pages 110 and following of the user guide of CORSIKA useful. They detail the structure of DATnnn files, as per page 25 of same document (footnote 32):
"To read this data set the FORTRAN programs corsikaread.f, corsikareadhistory.f rsp.corsikareadthin.f available in the src/utils/ subsubdirectory may be used."
I am trying also to read a corsika file, I used COAST but it only gives me the (id,x,y,e) of the shower. I still need to know the zenith and azimuth angle.
I have a corsikaread.f file in src/utils but there is no executable file.