Get multiple values in an xml file - regex

Question

<!-- someotherline -->
<add name="core" connectionString="user id=value1;password=value2;Data Source=datasource1.comapany.com;Database=databasename_compny" />
I need to grab the values in userid , password, source, database. Not all lines are in the same format.My desired result would be (username=value1,password=value2, DataSource=datasource1.comapany.com,Database=databasename_compny)
This regex seems little bit more complicated as it is more complicated. Please, explain your answer if possible.
I realised its better to loop through each line. Code I wrote so far
while read p || [[ -n $p ]]; do
#echo $p
if [[ $p =~ .*connectionString.* ]]; then
echo $p
fi
done <a.config
Now inside the if I have to grab the values.

Answer 1

For this solution I am considering:
Some lines can contain no data
No semi-colon ; is inside the data itself (nor field names)
No equal sign = is inside the data itself (nor field names)
A possible solution for you problem would be:
#!/bin/bash
while read p || [[ -n $p ]]; do
# 1. Only keep what is between the quotes after connectionString=
filteredLine=`echo $p | sed -n -e 's/^.*connectionString="\(.\+\)".*$/\1/p'`;
# 2. Ignore empty lines (that do not contain the expected data)
if [ -z "$filteredLine" ]; then
continue;
fi;
# 3. split each field on a line
oneFieldByLine=`echo $filteredLine | sed -e 's/;/\r\n/g'`;
# 4. For each field
while IFS= read -r field; do
# extract field name + field value
fieldName=`echo $field | sed 's/=.*$//'`;
fieldValue=`echo $field | sed 's/^[^=]*=//' | sed 's/[\r\n]//'`;
# do stuff with it
echo "'$fieldName' => '$fieldValue'";
done < <(printf '%s\n' "$oneFieldByLine")
done <a.xml
Explanations
General sed replacement syntax :
sed 's/a/b/' will replace what matches the regex a by the content of b
Step 1
-n argument tells sed not to output if no match is found. In this case this is useful to ignore useless lines.
^.* - anything at the beginning of the line
connectionString=" - literally connectionString="
\(.\+\)" - capturing group to store anything in before the closing quote "
.*$" - anything until the end of the line
\1 tells sed to replace the whole match with only the capturing group (which contains only the data between the quotes)
p tells sed to print out the replacement
Step 3
Replace ; by \r\n ; it is equivalent to splitting by semi-colon because bash can loop over line breaks
Step 4 - field name
Replaces literal = and the rest of the line with nothing (it removes it)
Step 4 - field value
Replaces all the characters at the beginning that are not = ([^=] matches all but what is after the '^' symbol) until the equal symbol by nothing.
Another sed command removes the line breaks by replacing it with nothing.