You want to add a timestamp line to a log file without deleting existing logs. Which Ruby code correctly does this?

hard📝 Application Q8 of 15

Ruby - File IO

AFile.open('log.txt', 'w') { |f| f.puts Time.now }

BFile.open('log.txt', 'r+') { |f| f.puts Time.now }

CFile.open('log.txt', 'r') { |f| f.puts Time.now }

DFile.open('log.txt', 'a') { |f| f.puts Time.now }

Step-by-Step Solution

Solution:

Step 1: Choose mode that preserves existing content
'a' mode appends data without deleting existing file content.
Step 2: Check other modes
'w' overwrites file, 'r' is read-only, 'r+' allows read/write but does not append automatically.
Final Answer:
File.open('log.txt', 'a') { |f| f.puts Time.now } -> Option D
Quick Check:
Append mode adds timestamp without deleting logs = B [OK]

Quick Trick: Use 'a' to add without erasing existing file data [OK]

Common Mistakes:

Master "File IO" in Ruby

9 interactive learning modes - each teaches the same concept differently

Want More Practice?

15+ quiz questions · All difficulty levels · Free

More Ruby Quizzes