path

#!/usr/bin/env python3

from os import path, sep, environ
from sys import argv, stdout

def chan_path(chan, path):
    if sep in path:
        # Strictly we would require a leading sep; as we do not have more than one
        # level of directories we simply treat `/chan/file` and `chan/file`
        # equivalently. The latter is easier to work with, so we normalize to it.
        # Thus the only time it is required to lead with sep is in the case where
        # only the root (i.e. `/`) or a chan (e.g. `/chan`) is specified, as
        # otherwise this would be interpreted as a file alone.
        if path.startswith(sep):
            path = path.lstrip(sep)
        splits = path.split(sep)
        chan = splits[0]
        name = ''.join(splits[1:])
    else:
        name = path
    return 'var/root/{}/{}'.format(chan, name).replace('..', '')

if __name__ == '__main__':
    chan = environ['CHAN']
    path = ' '.join(argv[1:])
    stdout.buffer.write(chan_path(chan, path).encode('utf-8'))