Ruby Ubuntu14.04上的gem中不存在Sass可执行文件

我已经在Ubuntu 14.04上安装了Sass，但找不到Sass等命令。我的安装历史记录如下：

# apt-get install ruby
Reading package lists... Done
Building dependency tree
Reading state information... Done
ruby is already the newest version.
ruby set to manually installed.
0 upgraded, 0 newly installed, 0 to remove and 105 not upgraded.

# gem install sass
Fetching: sass-3.4.5.gem (100%)
Successfully installed sass-3.4.5
Installing ri documentation for sass-3.4.5
1 gem installed

# which sass

# sass -v
The program 'sass' is currently not installed. You can install it by typing:
apt-get install ruby-sass

# gem list

*** LOCAL GEMS ***

bigdecimal (1.1.0)
bundler (1.6.2)
bundler-unload (1.0.2)
executable-hooks (1.3.2)
gem-wrappers (1.2.5)
io-console (0.3)
json (1.5.5)
minitest (2.5.1)
rake (0.9.2.2)
rdoc (3.9.5)
rubygems-bundler (1.4.4)
rvm (1.11.3.9)
sass (3.4.5)

# gem uninstall sass
Remove executables:
    sass, sass-convert, scss

in addition to the gem? [Yn]
Removing sass
Removing sass-convert
Removing scss
Successfully uninstalled sass-3.4.5

# gem install sass
Fetching: sass-3.4.5.gem (100%)
Successfully installed sass-3.4.5
Installing ri documentation for sass-3.4.5
1 gem installed

---

如果我安装了Ubuntu的ruby sass，它就可以工作了——你知道为什么gem安装不起作用吗？

我最好的猜测是某种路径问题——Ubuntu包的可执行文件正在你的路径上安装，而gem可执行文件却没有

尝试在系统上运行find/-name sass以查看可执行文件的安装位置