UNIX for Dummies Questions & Answers

-rw-r--r--    1 someuser   somegrp           61 Oct 22 16:01 abc.dat.20141022_160144
-rw-r--r--    1 someuser   somegrp           61 Oct 22 16:04 abc.dat.20141022_160144
-rw-r--r--    1 someuser   somegrp       260434 Oct 22 16:04 mno.dat.20141022_160509
-rw-r--r--    1 someuser   somegrp       761028 Oct 22 16:05 mno.dat.20141022_160509
-rw-r--r--    1 someuser   somegrp         1435 Oct 22 16:06 mno.dat.20141022_160509

# ls -1, as in one, list in one column
ls -1 |
        # Strip off the .whatever, group in A, then print all unique groups
        awk -F. -v OFS="." '$2 == "dat" { NF-- ; A[$0] } END { for(X in A) print X }' |
        # Sort the names
        sort |
        # Loop over each 
        while read PREFIX
        do
                # List everything beginning with ${PREFIX} in extended format, sorted by time
                ls -lt "${PREFIX}"*
        done | awk '/^total/ { print "" ; next } 1' # Strip off the 'total' lines

       --time-style=STYLE
              with -l, show times using style STYLE: full-iso, long-iso, iso,
              locale, +FORMAT.  FORMAT is interpreted like ‘date'; if FORMAT
              is FORMAT1<newline>FORMAT2, FORMAT1 applies to non-recent files
              and FORMAT2 to recent files; if STYLE is prefixed with ‘posix-',
              STYLE takes effect only outside the POSIX locale
-- excerpt from man ls, q.v.