udiff

Pure Ruby unified diff library. No external dependencies, no shelling out to diff.

Compatible with Diffy::Diff.new(a, b, diff: '-u').to_s.

Uses the Myers diff algorithm.

Add this line to your Gemfile:

gem "udiff"

require "udiff"

a = "foo\nbar\nbaz\n"
b = "foo\nqux\nbaz\n"

puts Udiff::Diff.new(a, b).to_s

 foo
-bar
+qux
 baz

By default, file headers (--- a / +++ b) and hunk headers (@@ ... @@) are not included. To include them:

puts Udiff::Diff.new(a, b, include_diff_info: true).to_s

--- a
+++ b
@@ -1,3 +1,3 @@
 foo
-bar
+qux
 baz

puts Udiff::Diff.new(a, b).to_s(:color)

Produces ANSI-colored output:

• Red: removed lines
• Green: added lines
• Cyan: hunk headers (@@...@@)
• Gray: file headers (---/+++)

# Show 1 line of context instead of the default 3
puts Udiff::Diff.new(a, b, context: 1).to_s