Question

I have two Ruby files:

db/migrate/20120920180336_create_admin_pages.rb
db/migrate/20120920150716_devise_create_users.rb

There’s a constant variable in this file: _create_admin_pages.rb

How can I find it in a file and make the following command work right?

gsub_file "db/migrate/*_create_admin_pages.rb", "t.boolean :published", "t.boolean :published, :default => false"

Answer 1

ruby -pe 'gsub("t.boolean :published", "t.boolean :published, :default => false")' < db/migrate/*_create_admin_pages.rb

Ruby can run with several options. Here the -pe option (actually two options) let Ruby execute this loop:

• Until no more input:
• read a line of input,
• run the string after -pe as code,
• print the result.

All using the implicit variable $_, the last read line.