# Finding the second highest version using bash array script and clean up files

The goal is to print the highest version and second highest version of the list of files. The version is based on the first three digit places of the version. For example, version 2.3.0.1 version is just 2.3.0 (ignoring the last digit).

Once it can print the highest version and the second highest version of the list, it should remove all other versions which will essentially clean up the folders in that location by only keeping the current and last version.

The EXAMPLE folders that I created are:

AAA_6.6.4.12.TEST
AAA_7.6.4.12.TEST
AAA_75.6.4.12.TEST
AAA_75.7.4.12.TEST
CCC_81.0.0.0.TEST
CCC_81.2.0.0.TEST
CCC_81.2.3.0.TEST
DDD_1.0.0.0.TEST
DDD_1.0.0.1.TEST
DDD_1.0.0.6.TEST
DDD_1.1.0.0.TEST
DDD_2.0.0.0.TEST
DDD_2.0.0.1.TEST
DDD_2.0.0.3.TEST
DDD_3.0.0.0.TEST


This is the array that I have to compute the highest and second highest version:

new_var=( $(for arr in "${var[@]}"
do
echo $arr done | sort) ) for folder in * do if [[$folder =~ ([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.[0-9]{1,3} ]]
then
if [[ "$new_var" < "${BASH_REMATCH[1]}.${BASH_REMATCH[2]}.${BASH_REMATCH[3]}" ]]
then
new_var="${BASH_REMATCH[1]}.${BASH_REMATCH[2]}.${BASH_REMATCH[3]}" fi else echo "failed" fi done; echo "The highest version is:$new_var"
echo "The second highest version is: ${new_var[-2]}"  This prints the highest version correctly. However, I don't know how to get the second highest version and I don't know how to go about removing the rest of the versions from the directory. • Can you show the expected/actual output for your test input? To me, this appears to be a simple job for sort+head, if the number of components in the version number remains constant. – Toby Speight Sep 18 '17 at 12:03 ## 2 Answers I think your approach is too complicated and esoteric with the use of BASH_REMATCH. Here goes my solution: versions_to_keep=($(find -maxdepth 1 ! -path . -type d -printf "%f\n"\
| sort -n -t '_' -k 2 | sort -n -m -t '.' -k 2,3 | tail -n 2)
)
highest_version=${versions_to_keep[-1]} second_highest_version=${versions_to_keep[-2]}
echo "The highest version is: ${highest_version:?}" echo "The second highest version is:${second_highest_version:?}"
find -maxdepth 1 ! -path . -type d ! -name "${highest_version}"\ ! -name "${second_highest_version}" -exec rm -rf {} +


Explanation:

• find -maxdepth 1 ! -path . -type d -printf "%f\n": find and print the basename of directories at most one level below and excluding the current directory .
• sort -n -t '_' -k 2: sort in numerical order by field 2, fields delimited by _
• sort -n -m -t '.' -k 2,3: sort in numerical order by fields 2 to 3, fields delimited by ., but take care to merge already sorted results
• tail -n 2: output the last 2 lines
• ${highest_version:?} and ${second_highest_version:?}: if either of those variables is null or unset, print an error message and abort the script
• find -maxdepth 1 ! -path . -type d ! -name "${highest_version}" ! -name "${second_highest_version}" -exec rm -rf {} +: find directories at most one level below the current directory whose basename patterns match neither ${highest_version} nor ${second_highest_version} and delete them

Actually, if you can guarantee the directory names are of the format XXX_a.b.c.d.TEST, you can combine the two sort into one: sort -n -t '.' -k 1.5,3, which starts the sort at character position 5 in field 1 and ends the sort at field 3. If you only want to delete empty directories, you can replace -exec rm -rf {} + with -delete.

### Unnecessary code

This part is completely unnecessary, you can safely delete it:

new_var=( $(for arr in "${var[@]}"
do
echo $arr done | sort) )  ### Possible bug Since the compared terms are strings, this will be a lexical comparison: [[ "$new_var" < "${BASH_REMATCH[1]}.${BASH_REMATCH[2]}.${BASH_REMATCH[3]}" ]]  That means that 9.0.0 will be higher than 81.2.3. If you want to make it a numeric comparison, then you need to rewrite it, comparing each term appropriately, which is trickier: w1=${BASH_REMATCH[1]}
w2=${BASH_REMATCH[2]} w3=${BASH_REMATCH[3]}
if ((w1 > v1 || w1 == v1 && w2 > v2 || w1 == v1 && w2 == v2 && w3 > w3))
then
v1=$w1 v2=$w2
v3=$w3 fi  ### Next steps For the steps you didn't implement yet, I recommend the following logic: 1. Put the list of folder names into an array. 2. Create a function that finds the index of the highest version, let's call it hIndex. Pass to the function the elements of the array. 3. Use the hIndex function to find the highest element, and then delete it. 4. Repeat the previous step. This will effectively remove the second highest element. Something like this: hIndex() { local i=0 index v1 v2 v3 w1 w2 w3 for item; do if [[$item =~ ([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.[0-9]{1,3} ]]
then
w1=${BASH_REMATCH[1]} w2=${BASH_REMATCH[2]}
w3=${BASH_REMATCH[3]} if ((w1 > v1 || w1 == v1 && w2 > v2 || w1 == v1 && w2 >= v2 && w3 > w3)) then v1=$w1
v2=$w2 v3=$w3
index=$i fi fi ((i++)) done echo$index
}

index1=$(hIndex "${folders[@]}")
echo the highest is index=$index1,${folders[$index1]} folders[$index1]=dummy

index2=$(hIndex "${folders[@]}")
echo the highest is index=$index2,${folders[$index2]} unset folders[$index1]
unset folders[$index2]  Notice that instead of deleting the highest value, I replaced with a dummy value. I did it this way because deleting a value from a Bash array does not shift the remaining values. Although the hIndex "${folders[@]}" will not see the deleted value, its index is still there, with a blank value, and the index returned by hIndex may be incorrect. Filling the gap with a suitable placeholder is a bit lazy, but it's simple enough, and it works.

In the end, after the dummy values are removed with unset, you have the folder names in folders except the highest and the 2nd highest. You could iterate over these elements to delete them.

• The objective is NOT to delete the highest and second highest value, it is to KEEP them both and delete the rest of the versions. Essentially the highest version (current) and last version (second highest) will be the only ones kept. – user126270 Dec 21 '16 at 16:12
• @user126270 The goal here is to delete the highest and second highest values from the array. Then, you can iterate over the remaining elements and delete them in the filesystem. I modified the end part a bit to clarify. – janos Dec 21 '16 at 16:18