gztee.py

#!/usr/bin/python
# encoding: UTF-8

from os import (
    close, open, read, write,
    O_WRONLY, O_APPEND, O_CREAT, O_EXCL, O_NOCTTY,
)
from sys import argv
from zlib import compressobj, DEFLATED, Z_DEFAULT_STRATEGY


Z_PARTIAL_FLUSH = 1
Z_FULL_FLUSH = 3
Z_FINISH = 4

if __name__ == '__main__':
    obj = compressobj(9, DEFLATED, 16 | 15, 8, Z_DEFAULT_STRATEGY)

    if len(argv) != 2:
        raise SystemExit('Usage: ' + argv[0] + ' /path/to/logfile.log.gz')

    out_fd = open(argv[1], O_WRONLY | O_APPEND | O_CREAT | O_EXCL | O_NOCTTY, 0o640)
    try:
        write(out_fd, obj.flush(Z_PARTIAL_FLUSH))
        try:
            while True:
                try:
                    block = read(0, 4096)
                except (EOFError, KeyboardInterrupt):
                    break
                else:
                    if not block:
                        break
                    else:
                        write(1, block)
                        write(out_fd, obj.compress(block))
                        write(out_fd, obj.flush(Z_PARTIAL_FLUSH))
        finally:
            write(out_fd, obj.flush(Z_FINISH))
    finally:
        close(out_fd)