Key Matching using shell - bash

Question

I wanted to see different type of answers I receive from you guys for the below problem. I am curious to see below problem being solved completely through array or any other matching (if there is any).
Below is the problem. Keeping Name as the key we need to print their various phone numbers in a line.
$cat input.txt
Name1, Phone1
Name2, Phone2
Name3, Phone1
Name4, Phone5
Name1, Phone2
Name2, Phone1
Name4, Phone1
O/P:
$cat output.txt
Name1,Phone1,Phone2
Name2,Phone2,Phone1
Name3,Phone1
Name4,Phone5,Phone1
I solved the above problem but I wanted to see a solving technique perhaps one that is more effective than me. I am not an expert in shell still at a beginner level. My code below:
$cat keyMatchingfunction.sh
while read LINE; do
var1=(echo "$LINE"|awk -F\, '{ print $1 }')
matching_line=(grep "$var1" output.txt|wc -l)
if [[ $matching_line -eq 0 ]]; then
echo "$LINE" >> output.txt
else
echo $LINE is already present in output.txt
grep -q -n "$var1" output.txt
line_no=(grep -n "$var1" output.txt|cut -d: -f1)
keymatching=(echo "$LINE"|awk -F\, '{ print $2 }')
sed -i "$line_no s/$/,$keymatching/" output.txt
fi
done

Answer 1

Try this:
awk -F', ' '{a[$1]=a[$1]","$2}END{for(i in a) print i a[i]}' input.txt
Output:
Name1,Phone1,Phone2
Name2,Phone2,Phone1
Name3,Phone1
Name4,Phone5,Phone1

Answer 2

With bash and sort:
#!/bin/bash
declare -A array # define associative array
# read file input.txt to array
while IFS=", " read -r line number; do
array["$line"]+=",$number"
done < input.txt
# print array
for i in "${!array[#]}"; do
echo "$i${array[$i]}"
done | sort
Output:
Name1,Phone1,Phone2
Name2,Phone2,Phone1
Name3,Phone1
Name4,Phone5,Phone1