emitter.py

#!/usr/bin/env python3

# Helper binary used by test_shell.py to print interleaved sequences
# of strings to stderr/stdout.

import itertools
import sys
from typing import Iterator, Sequence, Tuple, TypeVar

T = TypeVar('T')


def grouper(n: int, iterable: Sequence[T]) -> Iterator[Tuple[T, ...]]:
    "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
    args = [iter(iterable)] * n
    return itertools.zip_longest(*args)


if __name__ == '__main__':
    for mode, payload in grouper(2, sys.argv[1:]):
        if mode == 'e':
            print(payload, end='', file=sys.stderr)
            sys.stderr.flush()
        elif mode == 'o':
            print(payload, end='', file=sys.stdout)
            sys.stdout.flush()
        elif mode == 'r':
            # Big enough payload to exceed default chunk limit
            print("." * (4096 * 128), file=sys.stdout)
            sys.stdout.flush()
        else:
            raise RuntimeError('Unrecognized mode')