| 1 | 1 | def grep(pattern: str, flags: str, files: list[str]) -> str: |
| 2 | | pass |
| 2 | """ |
| 3 | Search files for lines matching a search string and return all matching lines. |
| 4 | |
| 5 | Args: |
| 6 | pattern (str): The string to search for. |
| 7 | flags (str): Flags for customizing the command's behavior. |
| 8 | files (list[str]): One or more files to search in. |
| 9 | |
| 10 | Returns: |
| 11 | str: All matching lines, possibly with file names and line numbers prepended. |
| 12 | |
| 13 | Edge Cases: |
| 14 | - Empty pattern: Matches every line |
| 15 | - Empty file: No lines to match |
| 16 | - File not found: Should be handled gracefully |
| 17 | - Multiple flags: All specified flags should be applied |
| 18 | - No matching lines: Return empty string |
| 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 comparison |
| 28 | search_pattern = pattern.lower() if case_insensitive else pattern |
| 29 | |
| 30 | # Initialize results |
| 31 | result_lines = [] |
| 32 | matching_files = set() |
| 33 | |
| 34 | # Edge Case: Empty files list |
| 35 | if not files: |
| 36 | return "" |
| 37 | |
| 38 | # Process each file |
| 39 | for filename in files: |
| 40 | try: |
| 41 | # Edge Case: File not found |
| 42 | with open(filename, 'r') as file: |
| 43 | lines = file.readlines() |
| 44 | except FileNotFoundError: |
| 45 | # According to typical grep behavior, we silently ignore missing files |
| 46 | # or we could raise an error - following typical behavior here |
| 47 | continue |
| 48 | |
| 49 | # Edge Case: Empty file |
| 50 | if not lines: |
| 51 | continue |
| 52 | |
| 53 | # Process each line |
| 54 | for line_num, line in enumerate(lines, 1): |
| 55 | # Prepare line for comparison |
| 56 | compare_line = line.lower() if case_insensitive else line |
| 57 | |
| 58 | # Determine if line matches |
| 59 | if exact_match: |
| 60 | matches = search_pattern == compare_line.rstrip('\n') |
| 61 | else: |
| 62 | matches = search_pattern in compare_line |
| 63 | |
| 64 | # Apply invert flag |
| 65 | if invert_match: |
| 66 | matches = not matches |
| 67 | |
| 68 | # If line matches, collect results |
| 69 | if matches: |
| 70 | matching_files.add(filename) |
| 71 | |
| 72 | # If we only want file names, we can break early |
| 73 | if files_only: |
| 74 | break |
| 75 | |
| 76 | # Build output line |
| 77 | output_line = "" |
| 78 | |
| 79 | # Add filename if multiple files |
| 80 | if len(files) > 1: |
| 81 | output_line += f"{filename}:" |
| 82 | |
| 83 | # Add line number if requested |
| 84 | if line_numbers: |
| 85 | output_line += f"{line_num}:" |
| 86 | |
| 87 | # Add the actual line |
| 88 | output_line += line |
| 89 | |
| 90 | result_lines.append(output_line) |
| 91 | |
| 92 | # Edge Case: -l flag - return only filenames |
| 93 | if files_only: |
| 94 | # Return filenames in the order they were found in the files list |
| 95 | ordered_matching_files = [f for f in files if f in matching_files] |
| 96 | return "\n".join(ordered_matching_files) + ("\n" if ordered_matching_files else "") |
| 97 | |
| 98 | # Edge Case: No matches |
| 99 | return "".join(result_lines) |
| 100 | |
| 101 | # Handled Edge Cases: Empty pattern, Empty file, File not found, Multiple flags, No matching lines, Empty files list |