The 'sed' utility is what you want. It can search and replace text using
regular expressions. You should be able to 'cat' the resin.conf file into sed, do the replacement, and redirect the output back to resin.conf, something like this:
Code:
cat resin.conf | sed -e 's/ABC/XYZ/' > resin.conf
where ABC is a regular expression matching what you want to find, and XYZ is what you want to replace it with. There's a
sed micro-primer in the
advanced bash guide that may help you figure out how to insert a variable name into a sed expression.