How to make gem install command only install when not installed or update needed

Question

i've read the documentation from rubygems site, but i guess the "gem install" command always reinstall, recompile everything, even if the same version already installed..

how to make gem install command only install when needed?

Answer 1

It looks like the --conservative flag will make the gem command do what you want.

gem install rake --conservative

From the documentation gem install --help:

--conservative Don't attempt to upgrade gems already meeting version requirement

Answer 2

You may want to use something external like gembundler to handle project’s gem installation.

If you must use rubygems directly for this, a command like

ruby -e "puts `gem install GEMTOINSTALL` if(`gem list --no-versions | grep GEMTOINSTALL`) == ''"

would do the job.