check *.tmp wether it's a zip or not

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

I'm quite happily using Archive::Zip, but what I'm missing is a test wether the file is a zip file or not.

I receive attached files (*.txt, *.log and *.zip) by email.
My Mailprogram now calls my perl-prg
and 'delivers' all attachements as tmp-files (/tmp/../uihm7934.tmp),
so I'm loosing the post-scripts to recognize wether it is a zip-file or not.

No I want to check if the actual file (kluai8qwz.tmp) is it a zip-file (-> continue) or not (->next).

Right now I try to access that file

    status = zip->read( $tmp );
[download]

and I get this (unnecessary) errormessage:

format error: can't find EOCD signature
        Archive::Zip::Archive::_findEndOfCentralDirectory('Archive::Zi
+p::Archive=HASH(0x85fd7ac)','IO::File=GLOB(0x85fd974)') called at /us
+r/lib/perl5/sit
e_perl/5.8.3/Archive/Zip.pm line 955
        Archive::Zip::Archive::readFromFileHandle('Archive::Zip::Archi
+ve=HASH(0x85fd7ac)','IO::File=GLOB(0x85fd974)','/tmp/kde-cas/kmailn0q
+acc.tmp') calle
d at /usr/lib/perl5/site_perl/5.8.3/Archive/Zip.pm line 929
        Archive::Zip::Archive::read('Archive::Zip::Archive=HASH(0x85fd
+7ac)','/tmp/kde-cas/kmailn0qacc.tmp') called at /home/QTS/bin/zipBarC
+.pl line 52
[download]

Well the Error_Code is set as well, but this would be enough.

Does anybody know a more elegant way of a zip-check?

Thanks in advance
Carl Carl

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Re: check *.tmp wether it's a zip or not by tomhukins (Curate) on Nov 26, 2004 at 11:04 UTC
You could use something like File::Type to check whether the file looks like an `application/zip` file or not, before passing it to Archive::Zip.	[reply] [d/l]
Re: check *.tmp wether it's a zip or not by guha (Priest) on Nov 26, 2004 at 11:17 UTC
My quick tests show that a zip file's first four bytes seem to be 50 4B 03 04 in hexadecimal notation. That should allow you to filter out most of the non-zip files. Then you could use your zip->read() in a block eval to trap those other files that starts with the magic byte sequence. However, consider this a hack to be used only if you can't find a better-founded idea. Update: Well it seems it couldn't be better founded. The byte sequence is described in the format documentation as the "Local file header signature".	[reply]
Re^2: check *.tmp wether it's a zip or not by Anonymous Monk on Nov 26, 2004 at 11:44 UTC
Thanks, for your replies, I've installed File::Type that works. But I've written to the author of Archive::Zip, that such a test might be usefull to include. Carl	[reply]
Re: check *.tmp wether it's a zip or not by Hena (Friar) on Nov 26, 2004 at 11:40 UTC
If you are using *nix, try command 'file'.	[reply]
Re: check *.tmp wether it's a zip or not by Anonymous Monk on Nov 26, 2004 at 10:57 UTC
hmm, I forgot to say that I tried`(-T $tmp)` but all tmp-files (that had been .log, .txt, *.zip) were recognized as non-plain/text files. Carl	[reply] [d/l]
Re: check *.tmp wether it's a zip or not by rev_1318 (Chaplain) on Nov 26, 2004 at 12:57 UTC
On would expect that wrapping the code in eval {...} would catch the error (at least, I would), but it doesn't. Anybody knows why? What am I missing here? Paul	[reply]
Re^2: check *.tmp wether it's a zip or not by fglock (Vicar) on Nov 26, 2004 at 13:29 UTC
Maybe the error was a `warn`ing, not a `die`: `$ perl -e ' eval { warn "xxx" } ' xxx at -e line 1. $ perl -e ' eval { die "xxx" } ' $` [download]	[reply] [d/l] [select]
Re^3: check *.tmp wether it's a zip or not by radiantmatrix (Parson) on Nov 26, 2004 at 15:18 UTC
In which case, one might consider a local `$SIG{__WARN__}` handler: `sub is_zip { #Load the file local $SIG{__WARN__} = sub { goto CONTINUE }; $status = $zip->read($file); CONTINUE: #Check $status }` [download] The code above is bad (it's an idea only), but the basic idea is to have a __WARN__ handler that supresses printing of the error and then branches to a `goto` tag outside itself, which keeps the default handler from being called. However, using mime-magic to determine the file type is probably better. `#Read data into $file if ($file =~ m/^\x50\x4B\x03\x04/) { #Parse as ZIP file } else { #Parse as something else }` [download] Or automate that type of task with the previously-mentioned File::Type module. radiantmatrix `require General::Disclaimer;` Perl is	[reply] [d/l] [select]
Re^3: check *.tmp wether it's a zip or not by guha (Priest) on Nov 26, 2004 at 15:34 UTC
`perl -e "{ local $SIG{__WARN__} = sub { die @_;};eval {warn 'xxx'}; pr +int 'a:'. $@}" __OUTPUT__ a:xxx at -e line 1.` [download] That is check $@ for success. If you only check the signature, which is what my quick check into File::Type confirmed that it is doing, there is a risk even if it is remote that another binary file could start with these magic bytes.	[reply] [d/l]