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Showing posts from November, 2007

How to get the schema version number out of your Rails migrations

When you want to revert your Rails migration you need the version number so that you can perform the rollback:rake db:migration VERSION=?One way is to access the database and take a look in the schema_info table to find the version number.

An easier way is to add an additional task to Rake (found via the Quoted-Printable):
namespace :db do
desc 'Print the current database migration version number'
task :version => :environment do
puts ActiveRecord::Migrator.current_version
end
endCopy this code into a file called db_version.rake and place it in the lib/tasks directory within your Rails application.

To find out the current version number, simply run:rake db:versionTechnorati Tags: , , , , ,

How to add system-wide environment variables to Ubuntu & Debian Linux

Following on from my last post on how to add shared libraries to Linux's system library path I wanted to share a related tip on system-wide environment variables.

Common reasons for doing this are setting your locale, setting the location of a Java installation or specifying the character set that your database is using (if you use Oracle then that would be the NLS_LANG environment variable). Debian actually has a policy against system-wide environment variables stating "a program must not depend on environment variables to get reasonable defaults" and suggests that all programs should have wrapper shell scripts to set the relevant variables.

Ignoring this sound advice I tried adding them to /etc/profile but this didn't work when ssh was used from a remote machine to execute some commands (I was using Capistrano).

I couldn't find a complete way to do it (it wasn't picked up by any start scripts in /etc/init.d) but I achieved the most success by placing my varia…