RVM的主要作用是方便的管理系統中的多個ruby版本而不至於混亂。

我們來看看如何安裝RVM，我使用的ubuntu12.04LTS。

準備工作

後面需要使用curl，用dpkg -s curl命令檢查一下系統中有沒有安裝

[email protected]:~$ dpkg -s curl
Package: curl
Status: install ok installed
Priority: optional
Section: web
Installed-Size: 338
Maintainer: Ubuntu Developers <[email protected]
 
>
Architecture: i386
Version: 7.22.0-3ubuntu4
Replaces: curl-ssl
Provides: curl-ssl
Depends: libc6 (>= 2.7), libcurl3 (>= 7.16.2-1), zlib1g (>= 1:1.1.4)
Description: Get a file from an HTTP, HTTPS or FTP server
 curl is a client to get files from servers using any of the supported
 protocols. The command is designed to work without user interaction
 or any kind of interactivity.
 .
 curl offers a busload of useful tricks like proxy support, user
 authentication, FTP upload, HTTP post, file transfer resume and more.
Homepage: http://curl.haxx.se
Original-Maintainer: Ramakrishnan Muthukrishnan <
 
[email protected]>

[email protected]:~$ dpkg -s curl
系統沒有安裝軟體包 curl，因而沒有相關的資訊。
使用 dpkg --info (= dpkg-deb --info) 來檢測打包好的檔案，
還可以通過 dpkg --contents (= dpkg-deb --contents) 來列出它們的內容。

安裝rvm

用rvm官方推薦的方式安裝curl -L get.rvm.io | bash -s stable

回顯提示我們，RVM被安裝在$HOME/.vrm中；並且需要在終端中載入指令碼$HOME/.rvm/scripts/rvm

[email protected]:~$ curl -L get.rvm.io | bash -s stable
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   185  100   185    0     0    144      0  0:00:01  0:00:01 --:--:--   906
100 10235  100 10235    0     0   3929      0  0:00:02  0:00:02 --:--:-- 10888
Downloading RVM from wayneeseguin branch stable
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   131  100   131    0     0     62      0  0:00:02  0:00:02 --:--:--   143
100 1124k  100 1124k    0     0   127k      0  0:00:08  0:00:08 --:--:--  269k

Installing RVM to /home/abbuggy/.rvm/
    RVM PATH line found in /home/abbuggy/.bashrc /home/abbuggy/.zshrc.
    RVM sourcing line found in /home/abbuggy/.bash_profile /home/abbuggy/.zprofile.

# RVM:  Shell scripts enabling management of multiple ruby environments.
# RTFM: https://rvm.io/
# HELP: http://webchat.freenode.net/?channels=rvm (#rvm on irc.freenode.net)
# Cheatsheet: http://cheat.errtheblog.com/s/rvm/
# Screencast: http://screencasts.org/episodes/how-to-use-rvm

# In case of any issues read output of 'rvm requirements' and/or 'rvm notes'

Installation of RVM in /home/abbuggy/.rvm/ is almost complete:

  * To start using RVM you need to run `source /home/abbuggy/.rvm/scripts/rvm`
    in all your open shell windows, in rare cases you need to reopen all shell windows.

# abbuggy,
#
#   Thank you for using RVM!
#   I sincerely hope that RVM helps to make your life easier and more enjoyable!!!
#
# ~Wayne

[[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" # This loads RVM into a shell session.

[[condition]]，兩層的方括號中間括著條件返回條件是不是真。-s是判斷給定的檔案是否存在的命令。這樣一來，不就是在[[ -s "$HOME/.vrm/scripts/vrm"]]判斷剛才安裝的RVM是否存在嗎？ 

接下來的&&符號是“短路的與”，當前面的條件是真的時候，執行後面的語句，返回這兩個語句是不是全是真。在這裡，利用了“短路”特性。也就是說當RVM已經安裝的話，執行後面的. "$HOME/.rvm/scripts/rvm"命令。這條命令和source "$HOME/.rvm/scripts/rvm"是一個意思：載入rvm的啟動指令碼。

#符號後面是註釋資訊。

使用RVM

剛才我們通過修改.bash_profile增加的內容需要重新開啟終端視窗時載入。我們有兩個選擇，一個是關閉當前的終端視窗重新開啟，另一個是在當前視窗執行一遍. "$HOME/.rvm/scripts/rvm"。

察看RVM的版本

[email protected]:~$ rvm -v

rvm 1.16.20 (stable) by Wayne E. Seguin <[email protected]>, Michal Papis <[email protected]> [https://rvm.io/]

通過rvm requirements命令，可以察看安裝各版本時候的前提條件。其中這句是需要關注的。這是安裝依賴的第三方包，沒有這個安裝不成功豈不是很悲劇？

Additional Dependencies:
# For Ruby / Ruby HEAD (MRI, Rubinius, & REE), install the following:
  ruby: /usr/bin/apt-get install build-essential openssl libreadline6 libreadline6-dev curl git-core zlib1g zlib1g-dev libssl-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt-dev autoconf libc6-dev ncurses-dev automake libtool bison subversion pkg-config

[email protected]:~$ rvm list

rvm rubies

# No rvm rubies installed yet. Try 'rvm help install'.

[email protected]:~$ rvm list known
# MRI Rubies
[ruby-]1.8.6[-p420]
[ruby-]1.8.7-p370
[ruby-]1.8.7[-p371]
[ruby-]1.9.1[-p431]
[ruby-]1.9.2-p180
[ruby-]1.9.2-p290
[ruby-]1.9.2-p318
[ruby-]1.9.2[-p320]
[ruby-]1.9.2-head
[ruby-]1.9.3-preview1
[ruby-]1.9.3-rc1
[ruby-]1.9.3-p0
[ruby-]1.9.3-p125
[ruby-]1.9.3-p194
[ruby-]1.9.3-p286
[ruby-]1.9.3-[p327]
[ruby-]1.9.3-head
[ruby-]2.0.0-preview1
ruby-head

[email protected]:~$ rvm install 1.9.3-head

[email protected]:~$ rvm list

rvm rubies

   ruby-1.8.7-p371 [ i686 ]
   ruby-1.9.3-head [ i686 ]

# Default ruby not set. Try 'rvm alias create default <ruby>'.

[email protected]:~$ rvm use ruby-1.9.3-head --default
Using /home/abbuggy/.rvm/gems/ruby-1.9.3-head

[email protected]:~$ ruby -v
ruby 1.9.3p327 (2012-11-10) [i686-linux]

[email protected]:~$ which ruby
/home/abbuggy/.rvm/rubies/ruby-1.9.3-head/bin/ruby

短路RVM

剛才是用RVM進行ruby版本管理，當然了通過其他渠道例如apt-get也可以安裝ruby，可以對RVM設定短路以便使用系統預設的ruby版本。

[email protected]:~$ rvm use system
Now using system ruby.
[email protected]:~$ ruby -v
ruby 1.8.7 (2011-06-30 patchlevel 352) [i686-linux]
[email protected]:~$ which ruby
/usr/bin/ruby

解除安裝RVM

不想玩了，我要解除安裝。這個命令會移除$HOME/.rvm目錄下面的所有東西即RVM管理的版本們。

rvm implode

也應該刪除$HOME/.bash_profile中增加的相關內容。