Ruby学习札记(3)- Ruby中gem的安装与卸载
Ruby学习札记(3)- Ruby中gem的安装与卸载
在Ruby中有gem包这种概念，类似PHP中的pear，相当于一种插件。具体可以Google一下。
（1）查看已经安装的gem
如果安装Ruby（我用的是Ruby1.9.2）时，勾选了“Add Ruby executables to your PATH”选项，那么可以在CMD中直接输入gem list列出本地已安装的gems。
C:/>gem list *** LOCAL GEMS *** minitest (1.6.0) rake (0.8.7) rdoc (2.5.8)
可以看到已经有3个gem。
如果安装时没有勾选，也没有关系，在“开始”菜单上，找到“Ruby 1.9.2-p180”->“Start Command Prompt with Ruby”，打开它，就会出现有Ruby环境的CMD。
（2）查询服务器端可用的gem
命令：gem query –remote，简写为gem q –R
结果如下：
*** REMOTE GEMS *** activerecord (0.8.4, 0.8.3, 0.8.2, 0.8.1, 0.8.0, 0.7.6, 0.7.5) Implements the ActiveRecord pattern for ORM. BlueCloth (0.0.4, 0.0.3, 0.0.2) BlueCloth is a Ruby implementation of Markdown, a text-to-HTML conversion tool for web writers. Markdown allows you to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML). captcha (0.1.2) Ruby/CAPTCHA is an implementation of the 'Completely Automated Public Turing Test to Tell Computers and Humans Apart'. cardinal (0.0.4) Ruby to Parrot compiler. cgikit (1.1.0) CGIKit is a componented-oriented web application framework like Apple Computers WebObjects. This framework services Model-View-Controller architecture programming by components based on a HTML file, a definition file and a Ruby source. progressbar (0.0.3) Ruby/ProgressBar is a text progress bar library for Ruby. It can indicate progress with percentage, a progress bar, and estimated remaining time. rake (0.4.0, 0.3.2) Ruby based make-like utility.
（3）在线安装gem
命令：gem install (gem-name)
回车之后，要等一等，无论是否安装成功，都会有提示信息。如果网速很慢，会一直停在这一行，这时就不要把CMD关了。
C:/Users/wesley_chen/dbi-0.4.3>gem install mysql Fetching: mysql-2.8.1-x86-mingw32.gem (100%) Successfully installed mysql-2.8.1-x86-mingw32 1 gem installed Installing ri documentation for mysql-2.8.1-x86-mingw32... Installing RDoc documentation for mysql-2.8.1-x86-mingw32...
安装好的gem默认位置在Ruby安装目录/ lib/ruby/gems/1.9.1，下面有4个目录cache、doc、gems和specification，根据目录名差不多知道大概的作用。
（4）离线安装gem
在http://rubygems.org/上会发布gem，有个技巧就是知道要安装的gem的名字，例如名字为deprecated的gem，那么在浏览器中输入http://rubygems.org/gems/deprecated（gem名字）就可以查询名为deprecated的gem所有版本，只要把“deprecated”换成其他gem的名字就可以了。
下载gem后，在CMD中切换到gem所在目录中，输入一下命令：
gem install ./(gem-name) --local
结果如下：
C:/Users/wesley_chen>gem install ./deprecated-3.0.0.gem --local Successfully installed deprecated-3.0.0 1 gem installed Installing ri documentation for deprecated-3.0.0... Installing RDoc documentation for deprecated-3.0.0... C:/Users/wesley_chen>gem list *** LOCAL GEMS *** deprecated (3.0.0) minitest (1.6.0) rake (0.8.7) rdoc (2.5.8)
（4）卸载gem
命令：gem uninstall (gem-name)
一般先用gem list查看一下，找到要卸载的gem的名字。
C:/>gem uninstall deprecated Successfully uninstalled deprecated-3.0.0
如果安装了多个版本，会出现以下提示
C:/Users/wesley_chen>gem list *** LOCAL GEMS *** dbi (0.4.3) deprecated (3.0.0, 2.0.1) minitest (1.6.0) rake (0.8.7) rdoc (2.5.8) C:/Users/wesley_chen>gem uninstall deprecated Select gem to uninstall: 1. deprecated-2.0.1 2. deprecated-3.0.0 3. All versions > 1 Successfully uninstalled deprecated-2.0.1
如果卸载的gem依赖其他的gem，会有以下提示信息
C:/Users/wesley_chen>gem uninstall deprecated You have requested to uninstall the gem: deprecated-3.0.0 dbi-0.4.3 depends on [deprecated (>= 2.0.0)] If you remove this gems, one or more dependencies will not be met. Continue with Uninstall? [Yn] y Successfully uninstalled deprecated-3.0.0