Linux shell get value of a field from a yml file

Question

I have a database.yml file like

development:   adapter: mysql2   encoding: utf8   database: d360   host: localhost   username: root   password: password  test:   adapter: mysql2   encoding: utf8   database: sample   host: localhost   username: root   password: password 

Now, I want value of database of test environment (that is sample for the YAML shown). How can we do that using sed?

Answer 1

That is fairly easy, not using sed, but with appropriate shell tools. First, if you need to preserve sample in a variable for later use, then something like the following will work using bash substring replacement to isolate sample on the Test:/database: line:

$ db=$(grep -A3 'test:' database.yml | tail -n1); db=${db//*database: /}; echo "$db" sample 

or for a shorter solution that you can dump to the command line, remove the variable and command substitution and use a tool like cut:

$ grep -A3 'test:' database.yml | tail -n1 | cut -c 13- sample 

or, with awk, simply:

$ grep -A3 'test:' database.yml | tail -n1 | awk '{ print $2}' sample 

All of the different ways can be used inside command substitution (i.e. var=$(stuff) ) to store sample in var, it is just a matter of which you would rather use. I think you get the idea.