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
560
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
1.6k
Content Negotiation for REST APIs
sferik
8
830
Writing Fast Ruby
sferik
622
60k
Mutation Testing with Mutant
sferik
5
1k
Other Decks in Programming
See All in Programming
The grand strategy of Ruby Parser
yui_knk
5
430
Dev ContainersとTestcontainers
bells17
3
100
Amazon Aurora Serverless v2が意外と高かった話と、AWS Database Migration Serviceの話
satoshi256kbyte
1
110
otelcol receiver 自作RTA / Pepabo Tech Conference #22 春のSREまつり
arthur1
0
1.1k
TypeScriptコードの漸進的改善 / Progressive Improvement of TypeScript Code
medley
1
460
TypeScriptとGraphQLで実現する 型安全なAPI実装 / TSKaigi 2024
hokaccha
5
2.9k
哲学史とモデリング
tanakahisateru
3
440
Open standards for building event-driven applications in the cloud
meteatamel
0
240
Unlocking Potential of Property Based Testing with Ractor
ohbarye
2
640
『WordPressコミュニティで学ぶ』OSS貢献の多様性
ippey
0
300
The Design of Everyday APIs - PyCon 2024
roguelynn
1
250
AppRouter Panel Talk
yosuke_furukawa
PRO
1
530
Featured
See All Featured
Building Your Own Lightsaber
phodgson
100
5.7k
Exploring the Power of Turbo Streams & Action Cable | RailsConf2023
kevinliebholz
8
3.5k
Thoughts on Productivity
jonyablonski
60
3.9k
Design by the Numbers
sachag
274
18k
How to Create Impact in a Changing Tech Landscape [PerfNow 2023]
tammyeverts
22
1.6k
[RailsConf 2023 Opening Keynote] The Magic of Rails
eileencodes
14
8.4k
A Tale of Four Properties
chriscoyier
153
22k
GraphQLとの向き合い方2022年版
quramy
33
13k
jQuery: Nuts, Bolts and Bling
dougneiner
60
7.2k
Statistics for Hackers
jakevdp
790
220k
StorybookのUI Testing Handbookを読んだ
zakiyama
13
4.7k
Creatively Recalculating Your Daily Design Routine
revolveconf
211
11k
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.