Hi...
I decided to see which printable ASCII characters would appear in a 'cat /path/to/packed_decimal_filename.ext' and came to the conclusion that without even a hint of a sample there is literally no way of helping...
#!/bin/bash
# EBCDIC.sh
# These are all the PRINTABLE ASCII ONLY characters generated by "EBCDIC" packed numbers.
# Note this does NOT include byte value 0, NULL; Ctrl characters; extended characters above decimal 128.
# Upper 4 bits BCD 2 to 7.
for high_nibble in {2..7}
do
# Lower 4 bits BCD 0 to 9.
for low_nibble in {0..9}
do
decimal=$(( low_nibble+(high_nibble*16) ))
printf "Low nibble = %d, high nibble = %d, decimal = %d, character = " $low_nibble $high_nibble $decimal
printf \\x$( printf "%02x" "$decimal" )".\n"
done
done
Results, OSX 10.14.3, default bash terminal:
Last login: Fri Mar 22 20:31:10 on ttys000
AMIGA:amiga~> cd Desktop/Code/Shell
AMIGA:amiga~/Desktop/Code/Shell> ./EBCDIC.sh
Low nibble = 0, high nibble = 2, decimal = 32, character = .
Low nibble = 1, high nibble = 2, decimal = 33, character = !.
Low nibble = 2, high nibble = 2, decimal = 34, character = ".
Low nibble = 3, high nibble = 2, decimal = 35, character = #.
Low nibble = 4, high nibble = 2, decimal = 36, character = $.
Low nibble = 5, high nibble = 2, decimal = 37, character = %.
Low nibble = 6, high nibble = 2, decimal = 38, character = &.
Low nibble = 7, high nibble = 2, decimal = 39, character = '.
Low nibble = 8, high nibble = 2, decimal = 40, character = (.
Low nibble = 9, high nibble = 2, decimal = 41, character = ).
Low nibble = 0, high nibble = 3, decimal = 48, character = 0.
Low nibble = 1, high nibble = 3, decimal = 49, character = 1.
Low nibble = 2, high nibble = 3, decimal = 50, character = 2.
Low nibble = 3, high nibble = 3, decimal = 51, character = 3.
Low nibble = 4, high nibble = 3, decimal = 52, character = 4.
Low nibble = 5, high nibble = 3, decimal = 53, character = 5.
Low nibble = 6, high nibble = 3, decimal = 54, character = 6.
Low nibble = 7, high nibble = 3, decimal = 55, character = 7.
Low nibble = 8, high nibble = 3, decimal = 56, character = 8.
Low nibble = 9, high nibble = 3, decimal = 57, character = 9.
Low nibble = 0, high nibble = 4, decimal = 64, character = @.
Low nibble = 1, high nibble = 4, decimal = 65, character = A.
Low nibble = 2, high nibble = 4, decimal = 66, character = B.
Low nibble = 3, high nibble = 4, decimal = 67, character = C.
Low nibble = 4, high nibble = 4, decimal = 68, character = D.
Low nibble = 5, high nibble = 4, decimal = 69, character = E.
Low nibble = 6, high nibble = 4, decimal = 70, character = F.
Low nibble = 7, high nibble = 4, decimal = 71, character = G.
Low nibble = 8, high nibble = 4, decimal = 72, character = H.
Low nibble = 9, high nibble = 4, decimal = 73, character = I.
Low nibble = 0, high nibble = 5, decimal = 80, character = P.
Low nibble = 1, high nibble = 5, decimal = 81, character = Q.
Low nibble = 2, high nibble = 5, decimal = 82, character = R.
Low nibble = 3, high nibble = 5, decimal = 83, character = S.
Low nibble = 4, high nibble = 5, decimal = 84, character = T.
Low nibble = 5, high nibble = 5, decimal = 85, character = U.
Low nibble = 6, high nibble = 5, decimal = 86, character = V.
Low nibble = 7, high nibble = 5, decimal = 87, character = W.
Low nibble = 8, high nibble = 5, decimal = 88, character = X.
Low nibble = 9, high nibble = 5, decimal = 89, character = Y.
Low nibble = 0, high nibble = 6, decimal = 96, character = `.
Low nibble = 1, high nibble = 6, decimal = 97, character = a.
Low nibble = 2, high nibble = 6, decimal = 98, character = b.
Low nibble = 3, high nibble = 6, decimal = 99, character = c.
Low nibble = 4, high nibble = 6, decimal = 100, character = d.
Low nibble = 5, high nibble = 6, decimal = 101, character = e.
Low nibble = 6, high nibble = 6, decimal = 102, character = f.
Low nibble = 7, high nibble = 6, decimal = 103, character = g.
Low nibble = 8, high nibble = 6, decimal = 104, character = h.
Low nibble = 9, high nibble = 6, decimal = 105, character = i.
Low nibble = 0, high nibble = 7, decimal = 112, character = p.
Low nibble = 1, high nibble = 7, decimal = 113, character = q.
Low nibble = 2, high nibble = 7, decimal = 114, character = r.
Low nibble = 3, high nibble = 7, decimal = 115, character = s.
Low nibble = 4, high nibble = 7, decimal = 116, character = t.
Low nibble = 5, high nibble = 7, decimal = 117, character = u.
Low nibble = 6, high nibble = 7, decimal = 118, character = v.
Low nibble = 7, high nibble = 7, decimal = 119, character = w.
Low nibble = 8, high nibble = 7, decimal = 120, character = x.
Low nibble = 9, high nibble = 7, decimal = 121, character = y.
AMIGA:amiga~/Desktop/Code/Shell> _
As one can see unless we have the EXACT format of the file then there is no way on earth to decode it.
There are some 'Ctrl' characters, ; binary 0 - NULL; a few in the _extended_ASCII_ region.