$ gem
RubyGems is a sophisticated package manager for Ruby.  This is a
basic help message containing pointers to more information.

  Usage:
    gem -h/--help
    gem -v/--version
    gem command [arguments...] [options...]

  Examples:
    gem install rake
    gem list --local
    gem build package.gemspec
    gem help install

  Further help:
    gem help commands            list all 'gem' commands
    gem help examples            show some examples of usage
    gem help platforms           show information about platforms
    gem help <COMMAND>           show help on COMMAND
                                   (e.g. 'gem help install')
    gem server                   present a web page at
                                 http://localhost:8808/
                                 with info about installed gems
  Further information:
    http://rubygems.rubyforge.org

$ gem help install
Usage: gem install GEMNAME [GEMNAME ...] [options] -- --build-flags [options]

  Options:
        --platform PLATFORM          Specify the platform of gem to install
    -v, --version VERSION            Specify version of gem to install
        --[no-]prerelease            Allow prerelease versions of a gem
                                     to be installed. (Only for listed gems)


  Deprecated Options:
    -u, --[no-]update-sources        Update local source cache


  Install/Update Options:
    -i, --install-dir DIR            Gem repository directory to get installed
                                     gems
    -n, --bindir DIR                 Directory where binary files are
                                     located
    -d, --[no-]rdoc                  Generate RDoc documentation for the gem on
                                     install
        --[no-]ri                    Generate RI documentation for the gem on
                                     install
    -E, --[no-]env-shebang           Rewrite the shebang line on installed
                                     scripts to use /usr/bin/env
    -f, --[no-]force                 Force gem to install, bypassing dependency
                                     checks
    -w, --[no-]wrappers              Use bin wrappers for executables
                                     Not available on dosish platforms
    -P, --trust-policy POLICY        Specify gem trust policy
        --ignore-dependencies        Do not install any required dependent gems
    -y, --include-dependencies       Unconditionally install the required
                                     dependent gems
        --[no-]format-executable     Make installed executable names match ruby.
                                     If ruby is ruby18, foo_exec will be
                                     foo_exec18
        --[no-]user-install          Install in user's home directory instead
                                     of GEM_HOME.
        --development                Install any additional development
                                     dependencies
        --conservative               Don't attempt to upgrade gems already
                                     meeting version requirement


  Local/Remote Options:
    -l, --local                      Restrict operations to the LOCAL domain
    -r, --remote                     Restrict operations to the REMOTE domain
    -b, --both                       Allow LOCAL and REMOTE operations
    -B, --bulk-threshold COUNT       Threshold for switching to bulk
                                     synchronization (default 1000)
        --clear-sources              Clear the gem sources
        --source URL                 Add URL as a remote source for gems
    -p, --[no-]http-proxy [URL]      Use HTTP proxy for remote operations


  Common Options:
    -h, --help                       Get help on this command
    -V, --[no-]verbose               Set the verbose level of output
    -q, --quiet                      Silence commands
        --config-file FILE           Use this config file instead of default
        --backtrace                  Show stack backtrace on errors
        --debug                      Turn on Ruby debugging


  Arguments:
    GEMNAME       name of gem to install

  Summary:
    Install a gem into the local repository

  Description:
    The install command installs local or remote gem into a gem repository.
    
    For gems with executables ruby installs a wrapper file into the executable
    directory by default.  This can be overridden with the --no-wrappers option.
    The wrapper allows you to choose among alternate gem versions using
    _version_.
    
    For example `rake _0.7.3_ --version` will run rake version 0.7.3 if a newer
    version is also installed.
    
    If an extension fails to compile during gem installation the gem
    specification is not written out, but the gem remains unpacked in the
    repository.  You may need to specify the path to the library's headers and
    libraries to continue.  You can do this by adding a -- between RubyGems'
    options and the extension's build options:
    
      $ gem install some_extension_gem
      [build fails]
      Gem files will remain installed in \
      /path/to/gems/some_extension_gem-1.0 for inspection.
      Results logged to /path/to/gems/some_extension_gem-1.0/gem_make.out
      $ gem install some_extension_gem -- --with-extension-lib=/path/to/lib
      [build succeeds]
      $ gem list some_extension_gem
    
      *** LOCAL GEMS ***
    
      some_extension_gem (1.0)
      $
    
    If you correct the compilation errors by editing the gem files you will need
    to write the specification by hand.  For example:
    
      $ gem install some_extension_gem
      [build fails]
      Gem files will remain installed in \
      /path/to/gems/some_extension_gem-1.0 for inspection.
      Results logged to /path/to/gems/some_extension_gem-1.0/gem_make.out
      $ [cd /path/to/gems/some_extension_gem-1.0]
      $ [edit files or what-have-you and run make]
      $ gem spec ../../cache/some_extension_gem-1.0.gem --ruby > \
                 ../../specifications/some_extension_gem-1.0.gemspec
      $ gem list some_extension_gem
    
      *** LOCAL GEMS ***
    
      some_extension_gem (1.0)
      $

  Defaults:
    --both --version '>= 0' --rdoc --ri --no-force
    --install-dir /home/gv/.gem/ruby/1.9.1