is_tarfile() returns True for a blank file

--------------------------------------------------
Hire the world's top talent on demand or became one of them at Toptal: https://topt.al/25cXVn
and get $2,000 discount on your first invoice
--------------------------------------------------

Music by Eric Matyas
https://www.soundimage.org
Track title: Hypnotic Puzzle3

--

Chapters
00:00 Is_tarfile() Returns True For A Blank File
01:24 Accepted Answer Score 1
01:42 Answer 2 Score 4
02:15 Answer 3 Score 1
02:36 Thank you

--

Full question
https://stackoverflow.com/questions/3058...

--

Content licensed under CC BY-SA
https://meta.stackexchange.com/help/lice...

--

Tags
#python

#avk47

ANSWER 1

Score 4

An empty tar file is a perfectly valid, and empty, tar file. Consider, at any Unix shell prompt:

$ touch foo.tar
$ ls -l foo.tar
-rw-r--r--  1 aleax  staff  0 Jun 16 18:49 foo.tar
$ tar tvf foo.tar 
$ tar xvf foo.tar

See? The empty foo.tar is a perfectly valid tar file for the Unix tar command -- it just has nothing to show or to unpack. It would be truly problematic if Python's tar handling differed so drastically from that of tar itself! What sentence in the docs led you to believe that such a problematic, headache-inducing incompatibility is part of the specs?

ACCEPTED ANSWER

Score 1

Try this at the command line:

$ touch emptyfile
$ tar -tvf emptyfile

No errors.

It looks like an empty file simply is a valid (but useless) TAR file.

ANSWER 3

Score 1

In fact, the behaviour of "is_tarfile" seems to have changed between Python 2.6 and 2.7. In Python 2.7, is_tarfile returns False for an empty file.

$ touch /tmp/foo.tar
$ python
Python 2.7.3 (default, Jul 24 2012, 11:41:40) 
[GCC 4.6.3 20120306 (Red Hat 4.6.3-2)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import tarfile
>>> print tarfile.is_tarfile("/tmp/foo.tar")
False
>>> 
$