[Bug-tar] Possible tar bug... or just clueless?

[Ian]

I'm working on a program that among other things wants to test a
tarfile.  I am doing this by running 'tar tf archive.tar' and checking
the exit status.

I have found that sometimes tar will exit with a 0 status for files
that are not tarfiles.  I'm not sure if this is a bug or occurs
because some simple files are actually degenerate cases of the tar
format.

I found this phenomenon on tar 1.14 (RHEL 4), but I've also verified
it with a freshly-built 1.18 version.

$ ./src/tar --version
tar (GNU tar) 1.18
Copyright (C) 2007 Free Software Foundation, Inc.
License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by John Gilmore and Jay Fenlason.
$ ./src/tar tf /etc/passwd
./src/tar: This does not look like a tar archive
./src/tar: Skipping to next header
./src/tar: Error exit delayed from previous errors
$ echo $?
2
$ rm -f foo
$ echo FOO > foo
$ ./src/tar tf foo
$ echo $?
0

I'm not subscribed to the list, just wanted to send a quick report, so
please cc me on replies.

Thanks,
Ian