| 1 | 1 | def grep(pattern: str, flags: str, files: list[str]) -> str: |
| 2 | | pass |
| 2 | """ |
| 3 | Search for a pattern in files and return matching lines. |
| 4 | |
| 5 | Args: |
| 6 | pattern: The string to search for |
| 7 | flags: String containing command line flags (-n, -l, -i, -v, -x) |
| 8 | files: List of file paths to search in |
| 9 | |
| 10 | Returns: |
| 11 | String containing matching lines, formatted according to flags |
| 12 | |
| 13 | Flags: |
| 14 | -n: Prepend line numbers |
| 15 | -l: Output only filenames with matches |
| 16 | -i: Case insensitive matching |
| 17 | -v: Invert matching (return non-matching lines) |
| 18 | -x: Match entire line only |
| 19 | """ |
| 20 | # Parse flags |
| 21 | line_numbers = '-n' in flags |
| 22 | files_only = '-l' in flags |
| 23 | case_insensitive = '-i' in flags |
| 24 | invert_match = '-v' in flags |
| 25 | exact_match = '-x' in flags |
| 26 | |
| 27 | # Prepare pattern for case-insensitive matching |
| 28 | search_pattern = pattern.lower() if case_insensitive else pattern |
| 29 | |
| 30 | # Results storage |
| 31 | results = [] |
| 32 | matched_files = set() |
| 33 | |
| 34 | # Process each file |
| 35 | for file_path in files: |
| 36 | try: |
| 37 | with open(file_path, 'r', encoding='utf-8') as file: |
| 38 | lines = file.readlines() |
| 39 | |
| 40 | # Process each line |
| 41 | for line_num, line in enumerate(lines, 1): |
| 42 | # Prepare line for comparison |
| 43 | compare_line = line.lower() if case_insensitive else line |
| 44 | |
| 45 | # Determine if line matches |
| 46 | if exact_match: |
| 47 | matches = (compare_line.rstrip('\n') == search_pattern) |
| 48 | else: |
| 49 | matches = (search_pattern in compare_line) |
| 50 | |
| 51 | # Apply invert flag |
| 52 | if invert_match: |
| 53 | matches = not matches |
| 54 | |
| 55 | # Edge Case: Handle empty pattern |
| 56 | if pattern == '': |
| 57 | matches = not invert_match # Empty pattern matches all lines unless inverted |
| 58 | |
| 59 | if matches: |
| 60 | matched_files.add(file_path) |
| 61 | |
| 62 | # If we only need file names, we can break early |
| 63 | if files_only: |
| 64 | break |
| 65 | |
| 66 | # Build output line |
| 67 | output_line = '' |
| 68 | |
| 69 | # Add filename prefix if multiple files |
| 70 | if len(files) > 1: |
| 71 | output_line += f'{file_path}:' |
| 72 | |
| 73 | # Add line number if requested |
| 74 | if line_numbers: |
| 75 | output_line += f'{line_num}:' |
| 76 | |
| 77 | # Add the actual line |
| 78 | output_line += line |
| 79 | |
| 80 | results.append(output_line) |
| 81 | |
| 82 | # Edge Case: Handle file not found |
| 83 | except FileNotFoundError: |
| 84 | # According to typical grep behavior, we silently ignore missing files |
| 85 | # or we could raise an error - following typical behavior here |
| 86 | pass |
| 87 | |
| 88 | # Edge Case: Handle permission errors |
| 89 | except PermissionError: |
| 90 | # Silently ignore files we can't read |
| 91 | pass |
| 92 | |
| 93 | # Edge Case: Handle -l flag (files only) |
| 94 | if files_only: |
| 95 | # Return only the names of files with matches, in the order they were found |
| 96 | output_files = [f for f in files if f in matched_files] |
| 97 | return '\n'.join(output_files) + ('\n' if output_files else '') |
| 98 | |
| 99 | # Edge Case: Handle no matches |
| 100 | if not results: |
| 101 | return '' |
| 102 | |
| 103 | # Edge Case: Handle trailing newlines |
| 104 | # Join all results, ensuring there's a newline at the end if there were any results |
| 105 | output = ''.join(results) |
| 106 | return output if output.endswith('\n') else output + '\n' if output else '' |
| 107 | |
| 108 | # Handled Edge Cases: Empty pattern, file not found, permission errors, -l flag, no matches, trailing newlines |