Split text file by filename/path comments (e.g. for writing LLM outputs to disk)

demux.py

import sys
import os
from typing import Dict
import re

def parse_files(content: str) -> Dict[str, str]:
    """Parse the input content into a dictionary of filepath -> content."""
    files = {}
    maybe_files = set()
    current_file = None
    current_content = []
    
    # Match both JS-style and Python-style comments for file paths
    file_pattern = re.compile(r'^(?://|#)\s+([a-zA-Z0-9./_-]+\.[a-zA-Z0-9]+)\s*$')
    weak_file_pattern = re.compile(r'^(?://|#)\s+(\S+)\s*$')
    
    for line in content.splitlines(keepends=True):
        # Check if line starts a new file
        match = file_pattern.match(line)
        weak_match = weak_file_pattern.match(line)
        if match:
            if current_file:
                assert current_file not in files, f"{current_file} appears more than once"
                # Save the previous file
                files[current_file] = ''.join(current_content)
            current_file = match.group(1)
            current_content = []
        elif current_file:
            # Add line to current file content
            current_content.append(line)

            if weak_match:
                maybe_files.add(weak_match.group(1))
        else:
            assert False

    # Don't forget to save the last file
    if current_file:
        files[current_file] = ''.join(current_content)
    
    return files, maybe_files

def ensure_directory(filepath: str) -> None:
    """Ensure all directories in the filepath exist."""
    directory = os.path.dirname(filepath)
    if directory:
        os.makedirs(directory, exist_ok=True)

def main() -> None:
    if len(sys.argv) != 2:
        print(f"Usage: {sys.argv[0]} <input_file>")
        sys.exit(1)
    
    input_file = sys.argv[1]
    
    try:
        with open(input_file, 'r') as f:
            content = f.read()
    except FileNotFoundError:
        print(f"Error: Could not find file '{input_file}'")
        sys.exit(1)
    
    files, maybe_files = parse_files(content)
    
    # Preview the files to be written
    for filepath, content in files.items():
        line_count = len(content.split('\n')) if content else "()"
        print(f"{filepath} ({line_count} lines)")
    
    if maybe_files:
        print("\nNOT detected as files:")
        for filepath in maybe_files:
            print(filepath)

    response = input("\nWrite? [y/N]")
    if response.lower() != 'y':
        print("Aborted.")
        sys.exit(0)
    
    # Write the files
    for filepath, content in files.items():
        try:
            ensure_directory(filepath)
            with open(filepath, 'w') as f:
                f.write(content)
        except IOError as e:
            print(f"Error writing {filepath}: {e}")
            sys.exit(1)

if __name__ == "__main__":
    main()

file_pattern will allow writes outside current directory, e.g. # /etc/foo.conf or # ../../../foo/bar.sh or # foo/../../../bar.sh...
Interactively prompting is good 👍, but consider also tightening against path traversal.