This is an extension to a question that was earlier posted on this forum:
I have task in which I need to pickup a set of files from a directory
depending on the following criteria:
Every month 6 files are expected to arrive at /test.
The files come with date timestamp and the latest file set for the month needs to be used
Suppose this is the set of files that present in the test directory
1. a_20080905_214058_200808.txt
2. b_20080905_214058_200808.txt
3. c_20080905_214058_200808.txt
4. d_20080905_214058_200808.txt
5. e_20080905_214058_200808.txt
6. f_20080905_214058_200808.txt
7. a_20080906_214058_200809.txt
8. b_20080906_214058_200809.txt
9. c_20080906_214058_200809.txt
10. d_20080906_214058_200809.txt
11. e_20080906_214058_200809.txt
12. f_20080906_214058_200809.txt
13. d_20080906_114058_200809.txt
14. e_20080906_114058_200809.txt
15. f_20080906_114058_200809.txt
Then
7. a_20080906_214058_200809.txt
8. b_20080906_214058_200809.txt
9. c_20080906_214058_200809.txt
10. d_20080906_214058_200809.txt
11. e_20080906_214058_200809.txt
12. f_20080906_214058_200809.txt files should be picked up.
Criteria 200809 is the latest month 20080906 is the latest date and 214058 is the latest date.
The criteria can be achieved using the following code

tr -s '_' ' ' < $LINE2 | \
sort -n -k 1.1,1.1 -k 2.1,2.8 -k 3.1,3.6 | \
awk '{ arr[$1]=$0 } END {for (i in arr) { print arr[i] } }' | \
tr '_' ' ' | sort > resultsfile
sed -e "s/ [ ]*/_/g" resultsfile > outfile #to replace spaces with '_' bcoz thats what the name of file is.
sed -e "s/^_//g" outfile >outfile2 #to remove '_' at the end of some lines
sed -e "s/_$//g" outfile2>outfile3 #to remove '_' at the beginning of some lines
grep -v "^$" outfile3 > newfilename
The problem is to understand the logic of the code below because the set of files has many '_' eg. The file may be
pra_hrt_cq_20080906_214058_200809.txt or rrt_cd_20080906_214058_200809.txt.
How to modify the above statement to achieve this. Another thing is I am creating many files o achieve this task and would like to avoid it.

tr -s '_' ' ' <  $LINE2 | \

  sort -n -k 1.1,1.1 -k 2.1,2.8 -k 3.1,3.6 | \
  awk '{ arr[$1]=$0 } END {for (i in arr) { print arr[i] } }' | \
  tr '_' ' ' | sort > resultsfile
sed -e "s/ [ ]*/_/g" resultsfile  > outfile #to replace spaces with '_' bcoz thats what the name of file is.
sed -e "s/^_//g" outfile >outfile2 #to remove '_' at the end of some lines
sed -e "s/_$//g" outfile2>outfile3 #to remove '_' at the beginning of some lines
grep -v "^$" outfile3 > newfilename

ls -t *.txt | head -n6

the ls wont work as the time stamp in the filename are not consistent with the actual file timestamps.

Taking the clue I am replacing the '_' with an unlikely string sequence and replacing then back at the end.

I still don't understand why you can't do this:

ls -r1 *_????????_??????_??????.txt|sort -t2 +1 -r|head -6

What does it give you? Why make it more difficult than what it is if you have the pattern already?!?

Actually there is not one pattern but six different patterns

given your quote above:
there's only ONE pattern:
'_n_n_n.txt' preceeded by ANYTHING. Isn't it true?

Hi

Thank you all for the suggestions.

I have made code changes as suggested and the results are awesome.

The FILENAME=/test/files.txt has all the patterns I want to keep.

The following code1 of epic proportions has been replaced by code2 although both are working fine.But shorter the better.

code1
*****************
#!/bin/ksh
#Directories
pathdir=/test
test_dir=/test
#Variables
pym=200812
ym=200901
#Imp Files
FILENAME=/test/files.txt
#Temp Files
LINE1=/test/files1$ym.txt
resultsfile=/test/files2$ym.txt
LINE3=/test/files3$ym.txt
usage(){
print process_test.sh - script to process test data
print "Usage: process_test.sh"
}
if test -f "$LINE1"
then
rm $LINE1
fi
cat $FILENAME | while read LINE
do
cd $test_dir
find . -name "$LINE$ym*$pym.txt" -print| while read obj
do
# echo "Inside DO loop"
echo $obj >> $LINE1
done
done
sed -e "s/^\.\///g" $LINE1| sed -e "s/_\([a-zA-Z]\)/kkk\1/g" > $LINE3
tr -s '_' ' ' < $LINE3| \
sort -n -k 1.1,1.1 -k 2.1,2.8 -k 3.1,3.6 | \
awk '{ arr[$1]=$0 } END {for (i in arr) { print arr[i] } }' | \
tr '_' ' ' | sort > $resultsfile
sed -e "s/ [ ]*/_/g" $resultsfile |sed -e "s/^_//g"|sed -e "s/_$//g"| \
grep -v "^$"|sed -e "s/kkk/_/g"| while read LINE4
do
echo "Process file : $LINE4"
done
rm $LINE1 $LINE3 $resultsfile
# end script

*****************

was replaced by

code2
**************

#!/bin/ksh
##########################################
#Directories
eagle_dir=/test
#Imp Files
FILENAME=/test/files.txt
usage(){
print process_test.sh - script to process test data
print "Usage: process_test.sh"
}
cat $FILENAME | while read LINE
do
ls -r1 "$test"/"$LINE"_????????_??????_??????.txt|sort -t2 +1 -r|head -1|while read obj
do
echo "Inside DO $LINE loop"
echo $obj
done
done
# end script