Simple `tee` alternative for operating systems without native tee command

tee.py

import argparse
import sys
from contextlib import ExitStack

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('filename', nargs='*')
    parser.add_argument('--append', '-a', action='store_true')
    args = parser.parse_args()

    print(args)

    with ExitStack() as stack:
        files = [stack.enter_context(
            open(fname, 'a' if args.append else 'w')) for fname in args.filename]
        print(files)
        for line in sys.stdin:
            print(line.rstrip())
            for fh in files:
                fh.write(line)

usage.md

The following command will output content from standard input to standard output, and will append the content into three destinations - test1.txt, test2.txt and test3.txt.

$ cat | python tee.py test{1,2,3}.txt --append