Replacing a value in a config file

Question

I have a file that looks like:

my.githash="asdfsadfdsf"
some.key=234
some.blue=abchello
russia.green="asdfdsf"

I want to replace the string for the key my.githash with an up to date git hash vlaue.

How can I use ruby to update my configuration file?

To get the git hash value I will be using:

git rev-parse HEAD

Answer 1

Using gsub you can replace a string using a regular expression match. In your case it's a little bit tricky because you don't know exactly the match.

Hence you can use

string.gsub(/(githash="(.+)")/) { $1.gsub($2, 'NEW_SHA') }

You can fetch the NEW_SHA running a shell command.

sha = `git rev-parse HEAD`
string.gsub(/(githash="(.+)")/) { $1.gsub($2, sha) }

and read the file from the file system

sha = `git rev-parse HEAD`
content = File.read('/path/to/fike')
content.gsub!(/(githash="(.+)")/) { $1.gsub($2, sha) }
File.write('/path/to/fike', content)

This is a very simple example. You can optimize it further. You can also use a single gsub , but it will require you to write twice the delimiters.

content.gsub!(/githash="(.+)"/, %Q{githash="#{sha}"})

Another (longer but perhaps more accurate) way is to write a simple parser that loads the file in a Hash parsing each line (as lines seems to follow a specific syntax), and then dumps the Hash back in a formatted file.