22. Find and Replace Across Multiple Files
1. Hello, World!
2. Rename Photos by Capture Date
3. Organize Downloads Folder by File Type
4. Delete Old Log Files Automatically
5. Find Duplicate Files Using MD5 Hashing
6. Generate Comprehensive File Inventory
7. Parse Web Server Logs for Performance Metrics
8. Extract Emails, URLs, and Phone Numbers from Text
9. Track Daily and Monthly Active Users from Apache Logs
10. Generate Formatted Text Reports with Column Alignment
11. Analyze Sales Transactions and Generate Revenue Reports
12. Clean and Validate CSV Data
13. Convert JSON API Responses to CSV
14. Parse and Validate Configuration Files
15. Build a CLI Calculator with Argument Parsing
16. Parse and Display Weather Data from JSON
17. Build a Simple Inventory System with Classes
18. Generate Markdown Table from CSV Data
19. Aggregate Sales Data by Time Period
20. Recursive Directory Size Calculator with Filtering
21. Parse and Transform Server Configuration
22. Find and Replace Across Multiple Files
23. Build a Simple Template Engine
24. CSV Data Validator with Business Rules
25. Build a Multi-Format Log Analyzer

Challenge

Problem

Batch text processing is essential for refactoring, configuration updates, and code migrations. This drill teaches you to search multiple files for patterns, perform replacements, and generate reports. You'll learn string pattern matching, counting occurrences, and batch processing—essential skills for building developer tools, automation scripts, and migration utilities.

Difficulty: Intermediate

Instructions

  1. Read configuration from config.json:
    • search: the pattern to find
    • replace: the replacement text
    • file_pattern: the type of files (for display)
  2. Read files data from files.json (simulates file contents)
  3. For each file:
    • Search for pattern
    • Count occurrences
    • Simulate replacement
  4. Print formatted report with:
    • Configuration used
    • Modified files with replacement counts
    • Summary statistics

Files

Editable
Read-only

Hints

Hint 1

JSON.parse(File.read(file)) loads JSON data

Hint 2

string.scan(pattern).length counts occurrences

Hint 3

Use a hash to track file path and count

Hint 4

Sort files alphabetically: array.sort_by { |f| f[:path] }

Hint 5

Check count > 0 to determine if file was modified

Hint 6

Sum counts for total replacements

Ruby 3.4

Provided Files (Read-only)

1. Correct find and replace report

Input: 
find_and_replace('config.json', 'files.json')
Expected Output: 
FIND AND REPLACE REPORT
==================================================
Search: TODO
Replace: FIXME
Files: *.txt
--------------------------------------------------
Modified: file1.txt (2 replacements)
Modified: subfolder/file3.txt (2 replacements)
--------------------------------------------------
SUMMARY
Files scanned: 3
Files modified: 2
Total replacements: 4

2. Counts occurrences correctly

Input: 
find_and_replace('config.json', 'files.json')
puts 'Counts OK'
Expected Output: 
FIND AND REPLACE REPORT
==================================================
Search: TODO
Replace: FIXME
Files: *.txt
--------------------------------------------------
Modified: file1.txt (2 replacements)
Modified: subfolder/file3.txt (2 replacements)
--------------------------------------------------
SUMMARY
Files scanned: 3
Files modified: 2
Total replacements: 4
Counts OK

3. Skips files without matches

Input: 
find_and_replace('config.json', 'files.json')
puts 'Skip OK'
Expected Output: 
FIND AND REPLACE REPORT
==================================================
Search: TODO
Replace: FIXME
Files: *.txt
--------------------------------------------------
Modified: file1.txt (2 replacements)
Modified: subfolder/file3.txt (2 replacements)
--------------------------------------------------
SUMMARY
Files scanned: 3
Files modified: 2
Total replacements: 4
Skip OK
+ 2 hidden test cases