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Building maintainable command-line tools with M...

Eric Hodel
September 09, 2016

Building maintainable command-line tools with MRuby

MRuby and mruby-cli makes it possible to ship single binary command-line tools that can be used without setup effort. How can we make these easy to write too?

Eric Hodel

September 09, 2016
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  1. About Me • Ruby commi?er • RubyGems commi?er • Rake

    commi?er • Author of many gems • On vacaEon
  2. Other mruby Talks 2016: Welcome to haconiwa 2016: Recent Advances

    in HTTP 2016: System calls hijacking with (m)ruby 2015: Making robot with mruby 2015: Building CLI Apps for Everyone 2014: MRuby as Development Plaborm for Payments 2014: MRuby on LEGO Mindstorms EV3 ® 2014: Resource Control Architecture scripEng with mruby
  3. build_config.rb • Which mrbgems to use • Which compiler to

    use • Library & include path • Can have many builds
  4. Using mruby-cli 1. Write MRuby 2. Compile 3. GOTO 1

    unless tests pass 4. Release executables
  5. Language Issues • No pre-defined globals • Some syntax bugs

    • No keyword arguments for def • Regexp replacements
  6. docker-compose run compile • Too long to type • run

    shell to debug • Unfamiliar environment
  7. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url =

    "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
  8. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url =

    "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
  9. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url =

    "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
  10. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url =

    "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
  11. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url =

    "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
  12. Simple Scripts • Minimum dependencies • Minimum opEons • One

    script per task • Very few large scripts
  13. Example Command class ConditionList < Command def execute results =

    api.send_request … results.each do |result| puts "…" end end
  14. mruby-curl • Most mature HTTP library • HTTP + HTTPS

    • Persistent connecEons • libcurl dependency
  15. mruby-mtest • Like minitest • Test subclass • test_* methods

    • setup / teardown • Remember: MTest::Unit.new.run