Step 2 – installing library dependencies
Your Sinatra projects will often use various software libraries for common tasks, such as HTML templating, sending e-mail, and communicating with databases. These libraries are called gems. If a gem is written purely in Ruby, installation is easy—you just have to download it.
Things are a little more complicated if the gem is written partly in Ruby and partly in C. These gems are said to have "native extensions"—you'll see these words in warning messages when you get around to installing your gems.
Sinatra install 1
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