How to unzip 'gzip compressed data, from FAT filesystem (MS-DOS, OS/2, NT),' using Python

Question

I am trying to unzip this archive file downloaded from iCloud.com using Python. None of the well-known methods work. I tried the following with Python 3:

using shutil.unpack_archive()
using Python’s gzip library
using Python’s zipfile library

When I inspected the file with Python’s magic library and xxd tool, it shows following output:

magic.from_file() => 'gzip compressed data, from FAT filesystem (MS-DOS, OS/2, NT), original size modulo 2^32 6670928'

xxd -l 4 ... => 1f8b 0800

What’s so special about a zip file created on FAT? How to unpack it?

Asked By: Mandarons

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Source

Answer 1

As your question title suggests, it’s not a zip file (despite the .zip filetype); it’s a gzip file. Try using the gzip module:

import zipfile
FN = "20210129_201905366.band.zip"
print(f"{FN} is a zip file: {zipfile.is_zipfile(FN)}")

import gzip
GZ = gzip.GzipFile(FN)
contents = GZ.read()
print(f"{FN} is a gzip file with length: {len(contents)}")
with open('ungzipped.zip', 'wb') as i:
    i.write(contents)
import shutil
shutil.unpack_archive('ungzipped.zip')
# This produces correct output file - 20210129_201905366.band

prints:

20210129_201905366.band.zip is a zip file: False
20210129_201905366.band.zip is a gzip file with length: 6670928

It turned out to be a zip file (20210129_201905366.band) inside gzip file (20210129_201905366.band.zip).

Answered By: codingatty

How to unzip 'gzip compressed data, from FAT filesystem (MS-DOS, OS/2, NT),' using Python

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