| 1 | 1 | def grep(pattern: str, flags: str, files: list[str]) -> str: |
| 2 | | pass |
| 2 | # Parse flags |
| 3 | line_numbers = '-n' in flags |
| 4 | files_only = '-l' in flags |
| 5 | case_insensitive = '-i' in flags |
| 6 | invert_match = '-v' in flags |
| 7 | exact_match = '-x' in flags |
| 8 | |
| 9 | # Prepare pattern for comparison |
| 10 | search_pattern = pattern.lower() if case_insensitive else pattern |
| 11 | |
| 12 | # Results storage |
| 13 | results = [] |
| 14 | matched_files = set() |
| 15 | |
| 16 | # Process each file |
| 17 | for filename in files: |
| 18 | try: |
| 19 | with open(filename, 'r', encoding='utf-8') as file: |
| 20 | # Edge Case: Handle files that cannot be read |
| 21 | lines = file.readlines() |
| 22 | except FileNotFoundError: |
| 23 | # Edge Case: Handle files that do not exist |
| 24 | continue |
| 25 | except IOError: |
| 26 | # Edge Case: Handle IO errors when reading files |
| 27 | continue |
| 28 | |
| 29 | # Process each line |
| 30 | for line_num, line in enumerate(lines, 1): |
| 31 | # Prepare line for comparison |
| 32 | compare_line = line.lower() if case_insensitive else line |
| 33 | |
| 34 | # Check for match based on exact_match flag |
| 35 | if exact_match: |
| 36 | is_match = (search_pattern == compare_line.rstrip('\n')) |
| 37 | else: |
| 38 | is_match = (search_pattern in compare_line) |
| 39 | |
| 40 | # Apply invert flag |
| 41 | if invert_match: |
| 42 | is_match = not is_match |
| 43 | |
| 44 | # If line matches criteria |
| 45 | if is_match: |
| 46 | # Edge Case: When -l flag is used, we only need to know which files match |
| 47 | if files_only: |
| 48 | matched_files.add(filename) |
| 49 | break # No need to check more lines in this file |
| 50 | else: |
| 51 | # Build output line |
| 52 | output_line = "" |
| 53 | # Add filename prefix if multiple files |
| 54 | if len(files) > 1: |
| 55 | output_line += f"{filename}:" |
| 56 | # Add line number if requested |
| 57 | if line_numbers: |
| 58 | output_line += f"{line_num}:" |
| 59 | # Add the actual line |
| 60 | output_line += line |
| 61 | results.append(output_line) |
| 62 | |
| 63 | # Edge Case: Handle -l flag output |
| 64 | if files_only: |
| 65 | # Return filenames in the order they were encountered |
| 66 | ordered_files = [f for f in files if f in matched_files] |
| 67 | return "\n".join(ordered_files) + ("\n" if ordered_files else "") |
| 68 | |
| 69 | # Edge Case: Handle empty results |
| 70 | return "".join(results) |
| 71 | |
| 72 | # Handled Edge Cases: files that cannot be read, files that do not exist, IO errors when reading files, -l flag usage, empty results |