Generic preprocessor

jpp.py

#!/usr/bin/env python
# coding: utf8
# GistID: 7893054

""" A generic preprocessor.

Replace `#include "<file>"` lines with file contents.
If the line starts with '//' then leave the include line in the output
for reference.

"""

import os
import re
import sys

include_regex = re.compile(
    r'''\s*(?P<comment>//)?\s*#include\s+["']?(?P<filename>[^'"]+)'''
)


def digest(line):
    """ Test a line against include_regex. If match, include the
    contents of the file inline.

    """
    m = include_regex.match(line)
    if m:
        fields = m.groupdict()
        filename = m.groupdict()['filename']
        with open(filename, 'rb') as fin:
            if fields['comment']:
                return line + fin.read()
            else:
                return fin.read()
    else:
        return line


def main():
    """Run main."""

    if len(sys.argv) > 1:
        fullpath = os.path.abspath(sys.argv[1].strip())
        directory, filename = os.path.split(fullpath)
        os.chdir(directory)
        with open(filename, 'rb') as fin:
            for line in fin:
                sys.stdout.write(digest(line))
    else:
        for line in sys.stdin:
            sys.stdout.write(digest(line))

    return 0

if __name__ == '__main__':
    main()