erb
TLDR
Process ERB template
$ erb [template.erb]
Process with Ruby variables$ erb -r [./vars.rb] [template.erb]
Output to file$ erb [template.erb] > [output.html]
Trim mode for cleaner output$ erb -T - [template.erb]
Print result without newline$ erb -P [template.erb]
SYNOPSIS
erb [options] [file...]
DESCRIPTION
erb processes ERB (Embedded Ruby) templates, allowing Ruby code to be embedded within text files. ERB is commonly used in Rails views and configuration file generation.
Templates use special tags: `<%= expr %>` outputs the expression result, `<% code %>` executes code without output, and `<%# comment %>` is for comments.
PARAMETERS
-r library
Require Ruby library before processing.-T mode
Trim mode: 0, 1, 2, or -.-P
Don't print newline after output.-e
Ignore RUBYOPT environment variable.-x
Print Ruby script instead of executing.-n
Print line numbers in output.-v
Verbose mode.--version
Show version.
TEMPLATE SYNTAX
$ <h1><%= @title %></h1>
<ul>
<% @items.each do |item| %>
<li><%= item %></li>
<% end %>
</ul>
<%# This is a comment %>
<ul>
<% @items.each do |item| %>
<li><%= item %></li>
<% end %>
</ul>
<%# This is a comment %>
TRIM MODES
$ -T 0 - No trimming
-T 1 - Trim lines ending with %>
-T 2 - Trim lines containing only <% %>
-T - - Trim newlines after -%>
-T 1 - Trim lines ending with %>
-T 2 - Trim lines containing only <% %>
-T - - Trim newlines after -%>
CAVEATS
Embedded Ruby executes with full permissions. Input should be trusted. Complex logic belongs in code, not templates. Whitespace handling may need trim mode adjustment.
HISTORY
ERB was created by Masatoshi Seki and included in Ruby's standard library. It became popular with Ruby on Rails as the default view template engine, though Rails now often uses alternatives like Slim or Haml.
