Skip to content

Instantly share code, notes, and snippets.

@krnwonseungee

krnwonseungee/Overview of Environmental Variables

Last active August 29, 2015 13:57
Show Gist options
  • Save krnwonseungee/9536759 to your computer and use it in GitHub Desktop.
Save krnwonseungee/9536759 to your computer and use it in GitHub Desktop.
Download ZIP
Raw
Overview of Environmental Variables
WHAT ARE ENVIRONMENTAL VARIABLES?
probably saw them in your challenge directories, under config.
such as ENV['BUNDLE_GEMFILE'] in the environment.rb file and
Environment variables are variables passed to programs by the command line or the graphical shell.
Though there are a number of environment variables that only affect the command line or graphical
shell itself (such as PATH or HOME), there are also several that directly affect how Ruby scripts execute.
basically, they are variables that capture a certain element in your environment.
HOW TO ACCESS THEM?
most commonly, system path variables.
Windows: SET
Mac & Linux: printenv
LANG=en_US.UTF-8
USER=apprentice
HOME=/Users/apprentice
on IRB, enter ENV and that will give you the list of environmental variables pertaining to Ruby.
"PWD" => "/Users/apprentice",
"EDITOR" => "/usr/local/bin/subl --wait",
"LANG" => "en_US.UTF-8",
"ITERM_PROFILE" => "Default",
"_system_arch" => "x86_64",
"PS1" => "\\n\\[\\e[0;38;5;32m\\]`_ps1_git_username``__git_ps1`\\040\\[\\e[m\\]\\w\\n\\[\\e[0;38;5;250m\\]$\\[\\e[m\\]\\040",
"_system_version" => "10.9",
"rvm_env_string" => "ruby-1.9.3-p448",
"rvm_version" => "1.22.15 (stable)",
"SHLVL" => "1",
"COLORFGBG" => "12;8",
"HOME" => "/Users/apprentice",
"rvm_ruby_string" => "ruby-1.9.3-p448",
"ITERM_SESSION_ID" => "w0t0p0",
"LOGNAME" => "apprentice",
"GEM_PATH" => "/Users/apprentice/.rvm/gems/ruby-1.9.3-p448:/Users/apprentice/.rvm/gems/ruby-1.9.3-p448@global",
"DISPLAY" => "/tmp/launch-poRAL6/org.macosforge.xquartz:0",
"RUBY_VERSION" => "ruby-1.9.3-p448",
"_system_name" => "OSX",
"__rvm_date" => "() { \\date \"$@\" || return $?\n}",
"_" => "/Users/apprentice/.rvm/rubies/ruby-1.9.3-p448/bin/irb",
"LINES" => "25",
"COLUMNS" => "80"
WHAT IS ENV, IN CONTEXT OF RUBY?
ENV is a hash-like accessor for environment variables. it's on Ruby Docs.
in order to access your variables and the values of those variables,
you include the word ENV in your command.
For example...
ENV[name] = value
ENV.each_pair (yields each key-value pair in a hash)
has_value?
RESOURCES
http://www.ruby-doc.org/core-2.1.0/ENV.html
http://ruby.about.com/od/rubyfeatures/a/envvar.htm
http://softimage.wiki.softimage.com/xsidocs/EnvVars_SettingandUsingEnvironmentVariables.htm
http://www.makeuseof.com/tag/what-are-environment-variables-how-can-i-use-them-windows/
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment