expect-ruby

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A Ruby library for automating interactive programs through POSIX pseudo-terminals. Start a child process, wait for text or regular expressions, send input, and manage timeouts, callbacks, and cleanup with Ruby objects and blocks.

RubyGems package: expect-pty. Requires Ruby 4.0.6+ on Linux or macOS.

Add the gem to your Gemfile:

gem "expect-pty", require: "expect/pty"

Then run bundle install, or install it directly with gem install expect-pty.

require "expect/pty"

program = "STDOUT.sync = true; print 'ready>'; STDIN.gets; puts 'done'"
Expect.spawn("ruby", "-e", program) do |session|
  prompt = session.expect("ready>", timeout: 5)
  raise "child did not become ready" unless prompt.matched?

  session.puts("continue")
  result = session.expect("done", timeout: 5)
  puts result.match if result.matched?
end

The block closes the session and reaps its child process, including when the block raises. Commands execute directly with separate argv entries, including a single executable string. Shell syntax requires explicit shell: true with one command string; never pass untrusted input into that string.

• Reusable automatic response rules for repeated confirmations, paging, and dynamic replies.
• Exact byte-string and Ruby Regexp matching, immutable results, callbacks, timeouts, and EOF handling.
• Explicit PTY sessions or borrowed IO sessions, with scoped cleanup and process status.
• Multi-session waits, IO forwarding, and interactive terminal handoff.
• Optional Logger diagnostics, receive transcripts, and streaming redaction.

• API reference
• Compatibility and behavior boundaries
• Migration guide
• Performance notes
• Examples

In a repository checkout, run the test suite and package checks with script/ci. The suite uses local PTYs, pipes, and sockets; SSH credentials are not required.

Licensed under the MIT License. Contributions are welcome in English or Chinese; see CONTRIBUTING.md.