Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Ruby Trivia 3
Search
Erik Berlin
December 03, 2015
Programming
0
570
Ruby Trivia 3
Presented at the Berlin Ruby User Group (RUG::B) on November 5, 2015.
Erik Berlin
December 03, 2015
Tweet
Share
More Decks by Erik Berlin
See All by Erik Berlin
Enumerator::Lazy
sferik
1
400
The Value of Being Lazy
sferik
3
600
Ruby Trivia 2
sferik
0
620
Ruby Trivia
sferik
2
1.1k
💀 Symbols
sferik
5
1.7k
Content Negotiation for REST APIs
sferik
8
840
Writing Fast Ruby
sferik
623
60k
Mutation Testing with Mutant
sferik
5
1k
Other Decks in Programming
See All in Programming
Porting mruby/c for the SNES (Super Famicom) - RubyKaigi 2024
gedorinku
0
2.1k
20240525_社内でPower Platform勉強会開いたら900人来た話
ponponmikankan
0
540
AIで生成したものをAIでチェックしてる話
ippey
0
130
Improved REXML XML parsing performance using StringScanner
naitoh
0
190
メッセージとイベントを中核に置いたシステム設計の有用性について
j5ik2o
PRO
8
600
コンパウンドプロダクト開発の質とスピードを支える Protobuf と Connect #アーキテクチャ_findy / Boosting Compound Product Development Efficiency with Protobuf and Connect
izumin5210
12
630
Why Spring Matters to Jakarta EE - And Vice Versa
ivargrimstad
0
110
AWS Infrastructure as Code の新機能を総まとめ! 2023.1-2024.5
konokenj
8
2.2k
GitHub Actionsの痒いところを埋めるサードパーティーランナー
dora1998
2
350
製造業ドメインにOneTeamでディープ・ダイブする組織設計・組織運営
i_senaz
1
190
新年度から始めるJava言語のファーストステップ2024
tatsuya1bm
0
150
Getting along with YAML comments with Psych
qnighy
2
1.4k
Featured
See All Featured
Documentation Writing (for coders)
carmenintech
60
4k
Principles of Awesome APIs and How to Build Them.
keavy
121
16k
How to train your dragon (web standard)
notwaldorf
76
5.3k
Designing on Purpose - Digital PM Summit 2013
jponch
111
6.5k
The Art of Programming - Codeland 2020
erikaheidi
43
12k
jQuery: Nuts, Bolts and Bling
dougneiner
60
7.2k
Mobile First: as difficult as doing things right
swwweet
217
8.6k
[RailsConf 2023 Opening Keynote] The Magic of Rails
eileencodes
14
8.4k
A Modern Web Designer's Workflow
chriscoyier
689
190k
Fireside Chat
paigeccino
22
2.7k
Why You Should Never Use an ORM
jnunemaker
PRO
51
8.7k
Cheating the UX When There Is Nothing More to Optimize - PixelPioneers
stephaniewalter
275
13k
Transcript
Ruby Trivia 3
What is the value of the global variable $_? Question
1:
The String last read by gets. Answer 1:
How can you list all global variables? Bonus Question:
How can you list all global variables? Bonus Question: Answer:
Use the Kernel#global_variables method.
How many global variables does Ruby define? global_variables.count Bonus Question:
How many global variables does Ruby define? global_variables.count Bonus Question:
Answer: 54.
What does Ruby’s -n switch do? Question 2:
Causes Ruby to assume the following loop around your script,
which makes it iterate over file name arguments like sed -n or awk. while gets ... end Answer 2:
What does Ruby’s -p switch do? Bonus Question:
Acts like the -n switch, but prints the value of
variable $_ at the each end of the loop. For example: ruby -p -e '$_.tr! "a-z", "A-Z"' < file Bonus Question:
What thread-local variable can only store four possible values? Question
3:
What thread-local variable can only store four possible values? Question
3: Hint #1: Those values are 0, 1, 2, and 3.
What thread-local variable can only store four possible values? Question
3: Hint #1: Those values are 0, 1, 2, and 3. Hint #2: The value is 0 by default and can only increase.
$SAFE Answer 3: Trick question because it looks like a
global variable, even though it behaves like a thread-local variable.
$SAFE Answer 3: There used to be $SAFE = 4
but it was removed in Ruby 2.1. Supposedly, it was only ever used by one company in Japan.
How can you check if an object is trusted? Bonus
Question:
How can you check if an object is trusted? Bonus
Question: Answer: Use the Kernel#tainted? method.
What happens if you do this? module Kernel def tainted?
return false end end Question 4:
The tainted? method will always return false, but Ruby will
still track tainted state via an internal FL_TAINT flag. Answer 4:
How can you mark a tainted object as safe? Question
5:
Kernel#untaint a.k.a. Kernel#trust $SAFE = 1 foo = gets.trust eval(foo)
Answer 5:
Thanks for playing! Follow @sferik on Twitter for more Ruby
trivia and practica.