This document discusses how to build command line interface (CLI) applications in Ruby. It introduces the Thor gem for building CLI apps with single commands and then discusses building interactive shell apps using a read-eval-print loop (REPL) and the GNU Readline library. The document provides examples of CLI apps, why they are useful, and tips for making better CLI apps, and concludes by showcasing a Facebook command line application built with these techniques.

1. Making CLI app with ruby

2. I'm Huy
@huydx
I'm software developer base in
Tokyo, Japan
Blogger at http://ktmt.github.io

3. What is CLI app
• CLI stand for command-line interface
• Some examples of CLI app
Git $git log --UI --word-diff
Grep $grep -c false /etc/passwd
mysql-cli >mysql
ruby-irb 2.1.3 :001 > 1 + 1 #2
single line
shell
interactive
shell

4. Why making CLI app
• We are programmers, we live in terminal
• Good CLI tool make our life easier
• Using terminal make us feel like a god

6. Introduce Thor
erikhuda/thor
"Thor is a simple and
efficient tool for building
self-documenting
command line utilities."
Using thor, we can build
single command line app with ease

7. Let's make a simple THOR app
(live coding)

8. But.....

9. Single line shell app
is somewhat boring~~~

10. Let's make interactive shell app
using REPL
• REPL stands for read–eval–print loop
• REPL can simply be a loop
!
while (line=gets) do
#do something with line
end
!
• Using REPL makes our app more
interactive

11. Writing complex
interactive shell from the
scratch is hard...

12. Introduce Readline
"The GNU Readline library
provides a set of functions for
use by applications that allow
users to edit command lines as
they are typed in. "
http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html
GNU readline binding for
ruby is a built in STL!!!!!!

13. What Readline capable of
• Customize-able prompt!!!
• Manage-able history
• Auto completion
• Interchange-able editing mode (vim, emacs)

14. Let's make a simple Readline app
(live coding)

15. Some tips to make better CLI app
• Do one thing
• Playing well with Others (streams, exit code)
• Have clear, concise purpose
• Perfect documentation

16. FACY
facebook command line app
huydx.com/facy

17. This is how my app looks like

18. REPO AT
HTTP://HUYDX.COM/FACY

19. Thank you for listening!!!