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 XML Configuration Files
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, handle different file encodings, and create backup copies. You'll learn glob patterns for file matching, regular expressions, in-place file editing, and safe file operations—essential skills for building developer tools, automation scripts, and migration utilities.

Difficulty: Intermediate

Instructions

  1. Read configuration from replace.txt:
    • Line 1: search pattern (can be regex)
    • Line 2: replacement text
    • Line 3: file pattern (e.g., '.txt' or '.rb')
  2. Find all files matching the pattern in current directory and subdirectories
  3. For each file:
    • Search for pattern
    • If found, create backup with .bak extension
    • Replace all occurrences
    • Count replacements
  4. Print report:
    'FIND AND REPLACE REPORT'
    '=' * 50
    'Search: [pattern]'
    'Replace: [replacement]'
    'Files: [pattern]'
    '-' * 50
    'Modified: [filename] (X replacements)'
    (for each modified file)
    '-' * 50
    'SUMMARY'
    'Files scanned: X'
    'Files modified: Y'
    'Total replacements: Z'

Files

Editable
Read-only

Hints

Hint 1

File.readlines(file) returns array of lines with newlines

Hint 2

Use .map(&:strip) to remove whitespace from each line

Hint 3

Dir.glob('**/' + pattern) searches recursively

Hint 4

File.file?(path) checks if path is a regular file (not directory)

Hint 5

string.scan(pattern).length counts occurrences

Hint 6

string.gsub(pattern, replacement) replaces all occurrences

Hint 7

Create backup: File.write(path + '.bak', content)

Hint 8

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

Provided Files (Read-only)

1. Replace TODO with FIXME in text files

Input: 
find_and_replace('replace.txt')
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. Replace in Ruby files

Input: 
find_and_replace('replace.txt')
Expected Output: 
FIND AND REPLACE REPORT
==================================================
Search: old_method
Replace: new_method
Files: *.rb
--------------------------------------------------
Modified: lib/helper.rb (1 replacements)
Modified: script1.rb (1 replacements)
Modified: script2.rb (2 replacements)
--------------------------------------------------
SUMMARY
Files scanned: 3
Files modified: 3
Total replacements: 4

3. No matches found

Input: 
find_and_replace('replace.txt')
Expected Output: 
FIND AND REPLACE REPORT
==================================================
Search: NOTFOUND
Replace: REPLACEMENT
Files: *.txt
--------------------------------------------------
(No files modified)
--------------------------------------------------
SUMMARY
Files scanned: 2
Files modified: 0
Total replacements: 0
+ 2 hidden test cases