~/test_dir🍺$ls -lrt
total 8
drwxr-xr-x  5 kk  Users   160B Apr 17 23:53 app1/
drwxr-xr-x  5 kk  Users   160B Apr 17 23:53 app2/
drwxr-xr-x  5 kk  Users   160B Apr 17 23:53 app3/
drwxr-xr-x  5 kk  Users   160B Apr 17 23:53 app4/
drwxr-xr-x  5 kk  Users   160B Apr 17 23:53 app5/

~/test_dir🍺$cd app1

~/test_dir/app1🍺$ls -rlt
total 0
drwxr-xr-x  2 kk  10677    64B Apr 19 14:16 release1/
drwxr-xr-x  2 kk  10677    64B Apr 19 14:16 release2/
drwxr-xr-x  2 kk  10677    64B Apr 19 14:16 release3/
drwxr-xr-x  2 kk  10677    64B Apr 19 14:16 release4/
drwxr-xr-x  2 kk  10677    64B Apr 19 14:17 release5/
drwxr-xr-x  2 kk  10677    64B Apr 19 14:17 relase23/
drwxr-xr-x  2 kk  10677    64B Apr 19 14:17 release8.9/
lrwxr-xr-x  1 kk  10677     8B Apr 19 14:18 Current@ -> release4

~/test_dir🍺ls -t1 | tail -n +3 | grep -v Current
relase23/
release5/
release4/
release3/
release2/
release1/

~/test_dir🍺ls -t1 | tail -n +3 | grep -v Current
relase23/
release5/
release4/
release3/
release2/
release1/

~/test_dir/app1🍺$ls -t1 | tail -n +3 | grep -v Current | xargs rm -r
~/test_dir/app1🍺$ls -rlt
total 0
drwxr-xr-x  2 kk  10677    64B Apr 19 14:17 release8.9/
lrwxr-xr-x  1 kk  10677     8B Apr 19 14:18 Current@ -> release4

#!/bin/bash
array=("app1" "app2" "app3" "app4" "app5")

for ((i=0;i<${#array[@]};i++))
do
app=${array[$i]}
echo "the app dir name is: $app"
cd ~/test_dir/$app
count=$(ls -t1 | tail -n +4 | grep -v Current | wc -l)
echo "number of directories deleted are:"
if [ $count == 0 ]
then
echo "Nothing to delete"
echo " "
else
ls -t1 | tail -n +4 | grep -v Current| xargs rm -r
fi
done
exit

~/test_dir/app1🍺$ls -t1 | tail -n +3 | grep -v Current | xargs rm -r
~/test_dir/app1🍺$ls -rlt
total 0
drwxr-xr-x  2 kk  10677    64B Apr 19 14:16 release4/
drwxr-xr-x  2 kk  10677    64B Apr 19 14:17 release8.9/
lrwxr-xr-x  1 kk  10677     8B Apr 19 14:18 Current@ -> release4

kept=0
stat -c "%Y %n %F" release* | sort -rn |
while read timestamp file type
do [[ directory == "$type" ]] || continue
   if (( kept++ < 2 ))
   then echo "Keeping $file ( $( date --date=@$timestamp ) )"
   else echo "Removing $file ( $( date --date=@$timestamp ) )"
        rm -fr $file
   fi
done