| 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): Space-separated string of flags (-n, -l, -i, -v, -x). |
| 8 | files (list[str]): List of file paths to search in. |
| 9 | |
| 10 | Returns: |
| 11 | str: Matching lines according to the specified flags. |
| 12 | |
| 13 | Edge Cases Handled: |
| 14 | - Empty files (no lines to process) |
| 15 | - Files that don't exist (skipped with no error) |
| 16 | - Empty pattern (matches all lines unless -x flag is used) |
| 17 | - No matching lines (returns empty string) |
| 18 | - Single file (no filename prefix in output) |
| 19 | - Multiple files (filename prefix added to each line) |
| 20 | - Combination of flags (-n with -l, -v with -x, etc.) |
| 21 | """ |
| 22 | # Parse flags |
| 23 | flag_list = flags.split() if flags else [] |
| 24 | line_numbers = '-n' in flag_list |
| 25 | files_only = '-l' in flag_list |
| 26 | case_insensitive = '-i' in flag_list |
| 27 | invert_match = '-v' in flag_list |
| 28 | exact_match = '-x' in flag_list |
| 29 | |
| 30 | # Prepare pattern for comparison |
| 31 | search_pattern = pattern.lower() if case_insensitive else pattern |
| 32 | |
| 33 | # Results storage |
| 34 | results = [] |
| 35 | matching_files = set() |
| 36 | |
| 37 | # Process each file |
| 38 | for file_path in files: |
| 39 | try: |
| 40 | with open(file_path, 'r', encoding='utf-8') as file: |
| 41 | # Edge Case: Empty files (no lines to process) |
| 42 | line_num = 0 |
| 43 | for line in file: |
| 44 | line_num += 1 |
| 45 | |
| 46 | # Prepare line for comparison |
| 47 | compare_line = line.lower() if case_insensitive else line |
| 48 | |
| 49 | # Determine if line matches |
| 50 | if exact_match: |
| 51 | # Edge Case: Exact match with line (strip newline for comparison) |
| 52 | matches = search_pattern == compare_line.rstrip('\n\r') |
| 53 | else: |
| 54 | # Edge Case: Substring match (empty pattern matches all) |
| 55 | matches = search_pattern in compare_line |
| 56 | |
| 57 | # Apply invert flag |
| 58 | if invert_match: |
| 59 | matches = not matches |
| 60 | |
| 61 | # If line matches criteria |
| 62 | if matches: |
| 63 | # Edge Case: Files only output (track matching files) |
| 64 | if files_only: |
| 65 | matching_files.add(file_path) |
| 66 | # Optimization: Break early when we only need file names |
| 67 | break |
| 68 | else: |
| 69 | # Build output line |
| 70 | output_line = "" |
| 71 | # Edge Case: Multiple files (add filename prefix) |
| 72 | if len(files) > 1: |
| 73 | output_line += f"{file_path}:" |
| 74 | # Edge Case: Line numbers (add line number after filename) |
| 75 | if line_numbers: |
| 76 | output_line += f"{line_num}:" |
| 77 | output_line += line |
| 78 | results.append(output_line) |
| 79 | except FileNotFoundError: |
| 80 | # Edge Case: Files that don't exist (skipped with no error) |
| 81 | continue |
| 82 | |
| 83 | # Edge Case: Files only output (return only file names) |
| 84 | if files_only: |
| 85 | # Return file names in the order they were specified |
| 86 | ordered_matching_files = [f for f in files if f in matching_files] |
| 87 | return '\n'.join(ordered_matching_files) + ('\n' if ordered_matching_files else '') |
| 88 | |
| 89 | # Edge Case: No matching lines (returns empty string) |
| 90 | return ''.join(results) |
| 91 | |
| 92 | # Handled Edge Cases: Empty files, files that don't exist, empty pattern, no matching lines, single file, multiple files, combination of flags |