How can I make a Ruby gem package copy files to arbitrary locations?

Question

Suppose you have a software package. You want to make it a gem, because gems are the de facto standard way to distribute anything in the Ruby world. Gems are great -- for libraries. But for real applications, the Rubygems system seems lacking. Only "recently" did they introduce a way to mark executables to be placed in somewhere in the system wide executable PATH. Unfortunately, Ruby gems still seems to be wanting in other aspects of software packaging, namely putting configuration files in places like /etc, or documentation under /usr/share/doc. Or is it? My question is:

Can I put instructions or code in a gemspec to have configuration installed into /etc, and documentation under some sensible, standardized place (like /usr/share/doc)? Or perhaps, as a workaround, can a post-install script be run to do these things?

For reference: the GemSpec specification.

Note that rubygems.org is down at the time of this writing. Here's the Google cache of that page: http://74.125.95.132/search?q=cache:JwJO6slR4BwJ:www.rubygems.org/read/chapter/20+http://www.rubygems.org/read/chapter/20%23page85&hl=en&ct=clnk&cd=1

If you examine the specification.rb file in the repo, and scroll down towards the end (search for ":section: Required gemspec attributes"), you can see what appear to be the currently supported attributes. I see nothing in there that looks like what I want.

Answer 1

The short answer: no

The long answer: You should not want/need to do this... gems are designed to be used as libraries... not as applications on their own (investigate your distros application package system for that type of thing). Plus, you cannot assume your gem will only be used "once"... in theory several projects/applications could include your gem, and while there maybe some specifics to your gem that preclude it to something that could be globally configured... you still wouldn't want to do that because of other architecture concerns such as developing/configuring your application to work in different phase environments (dev/test/stage/production). The best case you could end up in is just noting howto create the /etc/ config files in the README and include a utility application to prompt the user for the values.

Answer 2

You should not want/need to do this... gems are designed to be used as libraries... not as applications on their own (investigate your distros application package system for that type of thing).

You know that. And I know that. But "they" don't know that. For many moons, the regular queries and comments were: "Is there a gem?" "Can this be installed as a gem?" "Why don't you make a gem?" "I didn't install this because it's not a gem."

Right or not, desirable or not, Joe Rubyist expects everything to be gemified. Only old schoolers are familiar with and seem to tolerate "ruby setup.rb" type deals.

Anyway, my application really is a standalone application; I can hardly imagine anyone including this like a library. Maybe as part of a collection of applications, but... usage as a library seems pretty far-fetched, but if that day should ever come, I'll cross that bridge when I get to it (to help people with any conflicts which inclusion might bring).

And there is no "dev/test/stage/prod" distinction. It's a Plain Old App, you run it from command line.

Anyway, thanks for your comments, at least my assumptions are affirmed in that the Rubygems system doesn't provide a way to do this.

Answer 3

It's been a while -- what did you do in the end?

Stephan