Passing shell variable to awk in for-loop - regex

Question

I'm writing a script to print column and row numbers of cells which match a given string and then output it to a text file. The individual awk commands work fine in terminal and I've resolved other syntax issues, but .txt that is output still comes up empty. I think I have a problem with passing shell variables to awk.
#!/bin/bash
echo Literal or regex string to find:
read string
echo File path to find string match in:
read filename
echo "Matches for $string were found in the following cells:" > results.txt
for string in filename
do
awk -v awkvar="$string" -F"," '{for(i=1;i<=NF;i++){if ($i ~ /awkvar/){print i}}}' $filename >> results.txt | echo -e "\n" >> results.txt
awk -v awkvar="$string" '/awkvar/{print NR}' $filename >> results.txt | echo -e "\n" >> results.txt
done
Problem Resolved
I've rewritten the script as follows:
#!/bin/bash
# Prompt for input: 1. enter file name or path that you want searched; 2. enter the literal or regex string
echo File name or path to find matches in:
read file
echo Literal or regex string to find:
read string
# Define variable and test if any matches are to be found; if not, notification is sent to terminal, but if matches exist, their row numbers (as summary rows) and individual column numbers will be output to a .txt file in the home directory. NB: you need to escape minus symbol with brackets, [-], so that it's not confused with an invalid grep option!
matchesFound=$(cat $file | grep -E -c "$string")
if [ $matchesFound -eq 0 ];
then
echo "No matches exist."
else
printf "Summary Row No: \n`awk -v awkvar="$string" '$0 ~ awkvar{print NR}' $file`" > results_for_$string.txt
printf "\nInstance Column No: \n`awk -v awkvar="$string" -F"," '{for(i=1;i<=NF;i++){if ($i ~ awkvar){print i}}}' $file`" >> results_for_$string.txt
fi

Answer 1

You can't use awk variables inside regexp check pattern, try following instead. You could use index function of awk and to check if condition try without /../ way.
awk -v awkvar="$string" -F"," '{for(i=1;i<=NF;i++){if ($i ~ awkvar){print i}}}' $filename >> results.txt | echo -e "\n" >> results.txt
awk -v awkvar="$string" 'index($0,awkvar){print NR}' $filename >> results.txt | echo -e "\n" >> results.txt
This answer deals with only awk code shown by OP as per question, to fix it.