1.
RubyConf India 2012
Pune
Crafting Beautiful
Command Line Applications
using Ruby
Shishir Nikhil
@shishirdas @hyfather

2.
Shishir Das
@shishirdas
ThoughtWorks

3.
Nikhil Mungel
@hyfather
ThoughtWorks

4.
Why the command line?

5.
Why the command line?

6.
ey
heroku knife
puppet
pg_ctl mysql rails
git

7.
bash zsh powershell
ey
heroku knife
puppet
pg_ctl mysql rails
git

8.
ey
heroku knife
puppet
pg_ctl mysql rails
git
Developers
and
QAs

9.
Lightweight

10.
Lightweight

11.
Scriptable

12.
Consistent UX

13.
Consistent UX
*

14.
What makes a CLI app
good?

15.
The Luxury of
Ignorance

16.
~ > rails

17.
~ > rails
Usage: rails COMMAND [ARGS]
The most common rails commands are:
generate Generate new code (short-cut alias: "g")
console Start the Rails console (short-cut alias: "c")
server Start the Rails server (short-cut alias: "s")
~ >

18.
~ > rails generate

19.
~ > rails generate
Usage: rails generate GENERATOR [args] [options]
Please choose a generator below.
Rails:
assets
controller
generator
helper
integration_test
mailer
migration
model
observer
performance_test
plugin
~ >

20.
~ > ssh

21.
~ > ssh
usage: ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c
cipher_spec]
[-D [bind_address:]port] [-F configfile]
[-I pkcs11] [-i identity_file]
[-L [bind_address:]port:host:hostport]
[-l login_name] [-O ctl_cmd] [-o option] [-p port]
[-R [bind_address:]port:host:hostport] [-S ctl_path]
[-W host:port] [-w local_tun[:remote_tun]]
[user@]hostname [command]
~ >

22.
Least Astonishment

23.
~ > bundle

24.
~ > bundle
Fetching source index for https://rubygems.org/
Using rake (0.9.2.2)
Installing i18n (0.6.0)
Installing multi_json (1.0.4)
Installing activesupport (3.2.1)
Installing builder (3.0.0)
Installing activemodel (3.2.1)
Installing erubis (2.7.0)
~ >

25.
Reversibility

26.
~ > git commit -am "Added a new framework"

27.
~ > git commit -am "Added a new framework"
[master b4a2130] Added a new framework
2 files changed, 1012 insertions(+), 529 deletions(-)
~ >

28.
~ > git commit -am "Added a new framework"
[master b4a2130] Added a new framework
2 files changed, 1012 insertions(+), 529 deletions(-)
~ > git reset HEAD^

29.
~ > git commit -am "Added a new framework"
[master b4a2130] Added a new framework
2 files changed, 1012 insertions(+), 529 deletions(-)
~ > git reset HEAD^
Unstaged changes after reset:
M javascript/framework.js
M javascripts/support.js
~ >

30.
Config Files

31.
~ > knife cookbook upload apache2 -o /User/foo/cookbooks --
server-url http://chef-server:4000 --key /etc/chef/my.key --color
~ >

32.
~ > knife cookbook upload apache2 -o /User/foo/cookbooks --
server-url http://chef-server:4000 --key /etc/chef/my.key --color
~ >
~ > cat knife.rb
log_level :info
log_location STDOUT
node_name 'blitz'
client_key '/Users/shishir/.chef/blitz.pem'
validation_client_name 'chef-validator'
validation_key '/etc/chef/validation.pem'
chef_server_url 'http://10.10.100.202:4000'
cache_type 'BasicFile'
cache_options( :path => '/Users/shishir/.chef/checksums' )
~ >

33.
~ > knife cookbook upload apache2 -o /User/foo/cookbooks --
server-url http://chef-server:4000 --key /etc/chef/my.key --color
~ >
~ > cat knife.rb
log_level :info
log_location STDOUT
node_name 'blitz'
client_key '/Users/shishir/.chef/blitz.pem'
validation_client_name 'chef-validator'
validation_key '/etc/chef/validation.pem'
chef_server_url 'http://10.10.100.202:4000'
cache_type 'BasicFile'
cache_options( :path => '/Users/shishir/.chef/checksums' )
~ >
~ > knife cookbook upload apache2

34.
Graceful Failure

35.
~ > git pull

36.
~ > git pull
You asked me to pull without telling me which branch you
want to merge with, and 'branch.master.merge' in
your configuration file does not tell me, either. Please
specify which branch you want to use on the command line and
try again (e.g. 'git pull <repository> <refspec>').
See git-pull(1) for details.
If you often merge with the same branch, you may want to
use something like the following in your configuration file:
[branch "master"]
remote = <nickname>
merge = <remote-ref>
[remote "<nickname>"]
url = <url>
fetch = <refspec>
See git-config(1) for details.

37.
No hidden states

38.
Confirmations should
be scriptable

39.
~ > gem uninstall rspec

40.
~ > gem uninstall rspec
You have requested to uninstall the gem:
rspec-2.8.0
cucumber-1.1.4 depends on [rspec (>= 2.7.0)]
If you remove this gems, one or more dependencies will not be met.
Continue with Uninstall? [Yn] n

41.
~ > gem uninstall rspec
You have requested to uninstall the gem:
rspec-2.8.0
cucumber-1.1.4 depends on [rspec (>= 2.7.0)]
If you remove this gems, one or more dependencies will not be met.
Continue with Uninstall? [Yn] n
~ > gem uninstall -I rspec

42.
~ > gem uninstall rspec
You have requested to uninstall the gem:
rspec-2.8.0
cucumber-1.1.4 depends on [rspec (>= 2.7.0)]
If you remove this gems, one or more dependencies will not be met.
Continue with Uninstall? [Yn] n
~ > gem uninstall -I rspec
Successfully uninstalled rspec-2.8.0

43.
Honor Piping

44.
IO#tty?

45.
Why Ruby?

46.
Scripting Language

47.
Easy text
manipulation

48.
Good Abstractions

49.
Plethora of gems to
help you

50.
Examples to learn
from

51.
Structure of CLI
apps

52.
Input Execution Output

53.
Input Execution Output
STDIO = UI/UX

54.
Input

55.
Input
STDIN

56.
Input
ARGV/ENV
STDIN

57.
Input
ARGV/ENV
STDIN

58.
Input
ARGV/ENV
STDIN

59.
Input
OptionParser
ARGV/ENV
STDIN

60.
Input
OptionParser
ARGV/ENV
STDIN

61.
Input Libraries
OptionParser
ARGV/ENV
STDIN

62.
options = {}
OptionParser.new do |opts|
opts.banner = "Usage: example.rb [options]"
opts.on("-v", "--[no-]verbose", "Run verbosely") do |v|
options[:verbose] = v
end
end.parse!

63.
options = {}
OptionParser.new do |opts|
opts.banner = "Usage: example.rb [options]"
opts.on("-v", "--[no-]verbose", "Run verbosely") do |v|
options[:verbose] = v
end
end.parse!
~ > ./opt.rb --help
Usage: example.rb [options]
-v, --[no-]verbose Run verbosely

64.
options = {}
OptionParser.new do |opts|
opts.banner = "Usage: example.rb [options]"
opts.on("-v", "--[no-]verbose", "Run verbosely") do |v|
options[:verbose] = v
end
end.parse!
~ > ./opt.rb --help
Usage: example.rb [options]
-v, --[no-]verbose Run verbosely

65.
options = {}
OptionParser.new do |opts|
opts.banner = "Usage: example.rb [options]"
opts.on("-v", "--[no-]verbose", "Run verbosely") do |v|
options[:verbose] = v
end
end.parse!
~ > ./opt.rb --help
Usage: example.rb [options]
-v, --[no-]verbose Run verbosely

66.
options = {}
OptionParser.new do |opts|
opts.banner = "Usage: example.rb [options]"
opts.on("-v", "--[no-]verbose", "Run verbosely") do |v|
options[:verbose] = v
end
end.parse!
~ > ./opt.rb --help
Usage: example.rb [options]
-v, --[no-]verbose Run verbosely

67.
The Mixlib Suite

68.
class MyCLIApp
include Mixlib::CLI
option :config_file,
:short => "-c CONFIG",
:description => "Configuration file",
:required => true
end
~ > ./mycliapp.rb --help
Usage: ./mix.rb (options)
-c, --config CONFIG Configuration file (required)
-h, --help Show this message

69.
class MyCLIApp
include Mixlib::CLI
option :config_file,
:short => "-c CONFIG",
:description => "Configuration file",
:required => true
end
~ > ./mycliapp.rb --help
Usage: ./mix.rb (options)
-c, --config CONFIG Configuration file (required)
-h, --help Show this message

70.
class MyCLIApp
include Mixlib::CLI
option :config_file,
:short => "-c CONFIG",
:description => "Configuration file",
:required => true
end
~ > ./mycliapp.rb --help
Usage: ./mix.rb (options)
-c, --config CONFIG Configuration file (required)
-h, --help Show this message

71.
config.rb
server_url “http://server.remote”
username “elvis”
password “hotdog”

72.
config.rb
server_url “http://server.remote”
username “elvis”
password “hotdog”
class MyConfig
extend(Mixlib::Config)
server_url 'http://server.local'
username 'king'
password 'burger'
end
MyConfig.from_file(‘config.rb’)
irb> MyConfig.server_url
# ‘http://server.remote’

73.
config.rb
server_url “http://server.remote”
username “elvis”
password “hotdog”
class MyConfig
extend(Mixlib::Config)
server_url 'http://server.local'
username 'king'
password 'burger'
end
MyConfig.from_file(‘config.rb’)
irb> MyConfig.server_url
# ‘http://server.remote’

74.
Thor

75.
class Test < Thor
desc " FILE", "an example task"
method_option :delete,
:aliases => "-d",
:desc => "Delete the file"
def example(file)
end
end

76.
class Test < Thor
desc " FILE", "an example task"
method_option :delete,
:aliases => "-d",
:desc => "Delete the file"
def example(file)
end
end
~ > myapp help test:example
Usage:
thor test:example FILE
Options:
-d, [--delete=DELETE] # Delete the file after parsing it
an example task

77.
class Test < Thor
desc " FILE", "an example task"
method_option :delete,
:aliases => "-d",
:desc => "Delete the file"
def example(file)
end
end
~ > myapp help test:example
Usage:
thor test:example FILE
Options:
-d, [--delete=DELETE] # Delete the file after parsing it
an example task

78.
class Test < Thor
desc " FILE", "an example task"
method_option :delete,
:aliases => "-d",
:desc => "Delete the file"
def example(file)
end
end
~ > myapp help test:example
Usage:
thor test:example FILE
Options:
-d, [--delete=DELETE] # Delete the file after parsing it
an example task

79.
class Test < Thor
desc " FILE", "an example task"
method_option :delete,
:aliases => "-d",
:desc => "Delete the file"
def example(file)
end
end
~ > myapp help test:example
Usage:
thor test:example FILE
Options:
-d, [--delete=DELETE] # Delete the file after parsing it
an example task

80.
class Test < Thor
desc " FILE", "an example task"
method_option :delete,
:aliases => "-d",
:desc => "Delete the file"
def example(file)
end
end
~ > myapp help test:example
Usage:
thor test:example FILE
Options:
-d, [--delete=DELETE] # Delete the file after parsing it
an example task

81.
class Test < Thor
desc " FILE", "an example task"
method_option :delete,
:aliases => "-d",
:desc => "Delete the file"
def example(file)
end
end
~ > myapp help test:example
Usage:
thor test:example FILE
Options:
-d, [--delete=DELETE] # Delete the file after parsing it
an example task

82.
class Test < Thor
desc " FILE", "an example task"
method_option :delete,
:aliases => "-d",
:desc => "Delete the file"
def example(file)
end
end
~ > myapp help test:example
Usage:
thor test:example FILE
Options:
-d, [--delete=DELETE] # Delete the file after parsing it
an example task

83.
Testing

84.
Input Execution Output

85.
Input Execution Output

86.
Input Execution Output
Mostly third party libraries

87.
Input Execution Output
Test::Unit, rspec etc.

88.
Input Execution Output
System

89.
System
File System Network Process

90.
Isolated
Environments
Container
User Application
File
Memory Processes
System

91.
Streams & Signals

92.
STDOUT
STDIN
App
STDERR

93.
STDOUT
STDIN
App
STDERR

94.
STDOUT
STDIN
App
STDERR
STDOUT & STDERR
STDIN
App

95.
Mixlib::Shellout
> ls = Mixlib::ShellOut.new("ls")
> ls.run_command
> ls.stdout
“init.elnREADME.mdn”

96.
Mixlib::Shellout
> ls = Mixlib::ShellOut.new("ls")
> ls.run_command
> ls.stdout
“init.elnREADME.mdn”

97.
Plugin Architecture

98.
Hooks

99.
Logging

100.
GNU CLI standards
‘--version’ and ‘--help’
Input/Output Files --
-O for Output Files

101.
“CLI apps could be
the first consumers
”
of your services.

102.
“CLI apps could be
the first consumers
”
of your services.

103.
“CLI apps could be
the first consumers
”
of your services.
Testing Development
Cheap
No rich UI,
functional
Fast
tests

104.
Ideas
CLI app for a REST API: Github
SCM Plugins for Knife
Transform Rake scripts into first
class CLI apps
Shishir Nikhil
@shishirdas @hyfather

105.
Questions
Comments
Suggestions
Shishir Nikhil
@shishirdas @hyfather