gem install permission problem

qichunren@zhaobak:~> gem install hpricot
ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions into the /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8 directory.

Current login user is qichunren, and qichunre user have write permission with .gem dir.I would like to know why gem not install files into my home .gem dir first? Why my gem common first want to install files into /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8

Try setting GEM_HOME and GEM_PATH to ~/.gem,

For the current terminal session, just type:

export GEM_HOME=~/.gem
export GEM_PATH=~/.gem

If you want these to be set whenever you open a terminal, add the above commands to your ~/.bashrc file.

For a more comprehensive solution to setting up a custom ruby environment, see this tutorial from Site5KB, which describes using a .gemrc file.

For a systemwide Ruby install, become root. For example:

$ sudo gem install hpricot

However, the modern approach in many circumstances, including in development, is to use a tool that lets you easily install and use Ruby as a normal user. This lets you avoid having to become root. There are a few such tools, and the one I use is RVM.

# install rvm into your ~
$ \curl -sSL https://get.rvm.io | bash -s stable

# install latest version of ruby into your ~
$ rvm install ruby

# installs a gem into your ~
$ gem install $SOME_GEM_NAME