How to match two strings from separate lists - Posix Shell - linux

Question

I have a POSIX shell script that tries to find manual install paths for tomcat on an ubuntu (20.04) system. I run dpkg-query to make a list of installs that were installed using the package manager. Then I iterate over a list of common install paths. If any of the installs found using dpkg-query match, I need to exclude those from my discovery. But, I can't seem to figure out an efficient way to do this.
Code:
#/bin/sh
APP="Apache Tomcat"
# Common install paths to iterate over
set -- "/opt/" "/usr/share/" "/var/" "/var/lib/" "/usr/" "/usr/local/"
# Create exclusion list for managed installs from apt and yum
EXCLUSION_LIST=""
if [ -x "$(command -v dpkg-query)" ]; then
dpkg_check=$(dpkg-query -l | grep -Eo 'tomcat[0-9]?' | sort -u)
EXCLUSION_LIST=$dpkg_check
echo $EXCLUSION_LIST
# Check for manual installs
for _i in "$#"; do
find_tomcat=$(ls $_i | grep -E '^tomcat[0-9]{0,2}$')
excluded_list=$(echo $EXCLUSION_LIST)
for match in $excluded_list; do
if [ $find_tomcat == $match ]; then
echo "$match is excluded"
else
echo $_i$find_tomcat
done
done
else
echo "DPKG not found."
fi
Desired Output:
Install path of manual version not installed by the package manager.
E.g., /usr/share/tomcat

Answer 1

Observations:
The first line needs to start literally with the two characters #! to be a valid shebang
You are needlessly copying the same strings to multiple variables, in one place with a useless echo
Don't use upper case for your private variables; see Correct Bash and shell script variable capitalization
When to wrap quotes around a shell variable?
Don't parse ls output. Instead, I propose looping over wildcard matches in this case.
Your current logic seems to be basically saying, "if tomcat8 was installed by dpkg, don't print any tomcat8 paths." I'm guessing you actually want to avoid printing paths which are installed by a dpkg-installed tomcat* package, and print others.
Your dpkg-query -l command is slightly inexact, in that it will find not just package names, but also package descriptions which contain the search string. You can use dpkg-query -W instead, to only print package names and versions.
dpkg -L prints the actual paths installed by a set of packages.
Untested, but hopefully at least a step in the right direction.
#!/bin/sh
# Unused variable
# APP="Apache Tomcat"
if [ -x "$(command -v dpkg-query)" ]; then
exclusion_list=$(dpkg-query -W | sed -n 's/^\(tomcat[0-9]*\)\t[^\t].*/\1/p' | sort -u)
echo "$exclusion_list"
# Check for manual installs
for _i in "/opt" "/usr/share" "/var" "/var/lib" "/usr" "/usr/local"; do
for found in "$_i"/tomcat*; do
case $found in
*/tomcat | */tomcat[0-9] | */tomcat[0-9][0-9] ) ;;
*) continue;;
esac
found_dir=${found%/*}
if dpkg -L $exclusion_list | fgrep -qx "$found_dir"
then
echo "$match is excluded"
else
echo "$found"
fi
done
done
else
echo "DPKG not found."
fi