If your input file names are as described above and you want them sorted by year, month, day, and time; one of the following should work for you.

When there are just two files in the current directory and both files are from the same year, a simple:

Code:

echo *

will give you the two filenames to be processed in the correct order. If the files may be from different years, try:

Code:

ls -f | sort -t_ -k 5,5 -k 3,4 -k6,6

If your output file is also in the same directory (and has a name that doesn't start with Aggr, you can use:

Code:

ls -f Aggr* | sort -t_ -k 5,5 -k 3,4 -k6,6

If there are a bunch of these files in the directory and you just want the last two, you can use:

Code:

ls -f Aggr* | sort -t_ -k5,5 -k3,4 -k6,6 | tail -n2

If you have other files with names starting with Aggr (such as your output files), but they have a slightly different name format, you can use:

Code:

ls -f Aggr_New_[0-9][0-9]_[0-9][0-9]_[0-9][0-9][0-9][0-9]_[0-9][0-9][0-9][0-9].txt |
        sort -t_ -k5,5 -k3,4 -k6,6 | tail -n2

If you keep just giving us bits and pieces we continue to waste time trying to figure out what you're trying to do.

PLEASE, give a complete specification of your input and output requirements!