WWhhyy iiss mmyy zziipp ffiillee ssoo bbiigg??
QQ:: My zip file is actually bigger than what I stored in it! Why?
AA:: Some things to make sure of:
Make sure that you are requesting COMPRESSIONDEFLATED if you are
storing strings.
$member->desiredCompressionMethod( COMPRESSIONDEFLATED );
Don't make lots of little files if you can help it.
Since zip computes the compression tables for each member, small
members without much entropy won't compress well. Instead, if
you've got lots of repeated strings in your data, try to combine
them into one big member.
Make sure that you are requesting COMPRESSIONSTORED if you are storing
things that are already compressed.
If you're storing a .zip, .jpg, .mp3, or other compressed file in a
zip, then don't compress them again. They'll get bigger.
SSaammppllee ccooddee??
QQ:: Can you send me code to do (whatever)?
AA:: Have you looked in the "examples/" directory yet? It contains:
examples/calcSizes.pl - How to find out how big a Zip file will be
before writing it
examples/copy.pl - Copies one Zip file to another
examples/extract.pl - extract file(s) from a Zip
examples/mailZip.pl - make and mail a zip file
examples/mfh.pl - demo for use of MockFileHandle
examples/readScalar.pl - shows how to use IO::Scalar as the source
of a Zip read
examples/selfex.pl - a brief example of a self-extracting Zip
examples/unzipAll.pl - uses Archive::Zip::Tree to unzip an entire
Zip
examples/updateZip.pl - shows how to read/modify/write a Zip
examples/updateTree.pl - shows how to update a Zip in place
examples/writeScalar.pl - shows how to use IO::Scalar as the
destination of a Zip write
examples/writeScalar2.pl - shows how to use IO::String as the
destination of a Zip write
examples/zip.pl - Constructs a Zip file
examples/zipcheck.pl - One way to check a Zip file for validity
examples/zipinfo.pl - Prints out information about a Zip archive
file
examples/zipGrep.pl - Searches for text in Zip files
examples/ziptest.pl - Lists a Zip file and checks member CRCs
examples/ziprecent.pl - Puts recent files into a zipfile
examples/ziptest.pl - Another way to check a Zip file for
validity
CCaann''tt RReeaadd//mmooddiiffyy//wwrriittee ssaammee ZZiipp ffiillee
QQ:: Why can't I open a Zip file, add a member, and write it back? I get
an error message when I try.
AA:: Because Archive::Zip doesn't (and can't, generally) read file
contents into memory, the original Zip file is required to stay around
until the writing of the new file is completed.
The best way to do this is to write the Zip to a temporary file and
then rename the temporary file to have the old name (possibly after
deleting the old one).
Archive::Zip v1.02 added the archive methods "overwrite()" and
"overwriteAs()" to do this simply and carefully.
See "examples/updateZip.pl" for an example of this technique.
FFiillee ccrreeaattiioonn ttiimmee nnoott sseett
QQ:: Upon extracting files, I see that their modification (and access)
times are set to the time in the Zip archive. However, their creation
time is not set to the same time. Why?
AA:: Mostly because Perl doesn't give cross-platform access to creation
time. Indeed, many systems (like Unix) don't support such a concept.
However, if yours does, you can easily set it. Get the modification
time from the member using "lastModTime()".
CCaann''tt uussee AArrcchhiivvee::::ZZiipp oonn ggzziipp ffiilleess
QQ:: Can I use Archive::Zip to extract Unix gzip files?
AA:: No.
There is a distinction between Unix gzip files, and Zip archives that
also can use the gzip compression.
Depending on the format of the gzip file, you can use Compress::Zlib,
or Archive::Tar to decompress it (and de-archive it in the case of Tar
files).
You can unzip PKZIP/WinZip/etc/ archives using Archive::Zip (that's
what it's for) as long as any compressed members are compressed using
Deflate compression.
AAdddd aa ddiirreeccttoorryy//ttrreeee ttoo aa ZZiipp
QQ:: How can I add a directory (or tree) full of files to a Zip?
AA:: You can use the Archive::Zip::addTree*() methods:
use Archive::Zip;
my $zip = Archive::Zip->new();
# add all readable files and directories below . as xyz/*
$zip->addTree( '.', 'xyz' );
# add all readable plain files below /abc as def/*
$zip->addTree( '/abc', 'def', sub { -f && -r } );
# add all .c files below /tmp as stuff/*
$zip->addTreeMatching( '/tmp', 'stuff', '\.c$' );
# add all .o files below /tmp as stuff/* if they aren't writable
$zip->addTreeMatching( '/tmp', 'stuff', '\.o$', sub { ! -w } );
# add all .so files below /tmp that are smaller than 200 bytes as stuff/*
$zip->addTreeMatching( '/tmp', 'stuff', '\.o$', sub { -s < 200 } );
# and write them into a file
$zip->writeToFileNamed('xxx.zip');
EExxttrraacctt aa ddiirreeccttoorryy//ttrreeee
QQ:: How can I extract some (or all) files from a Zip into a different
directory?
AA:: You can use the Archive::Zip::extractTree() method: ??? ||
# now extract the same files into /tmpx
$zip->extractTree( 'stuff', '/tmpx' );
UUppddaattee aa ddiirreeccttoorryy//ttrreeee
QQ:: How can I update a Zip from a directory tree, adding or replacing
only the newer files?
AA:: You can use the Archive::Zip::updateTree() method that was added in
version 1.09.
ZZiipp ttiimmeess mmiigghhtt bbee ooffff bbyy 11 sseeccoonndd
QQ:: It bothers me greatly that my file times are wrong by one second
about half the time. Why don't you do something about it?
AA:: Get over it. This is a result of the Zip format storing times in DOS
format, which has a resolution of only two seconds.
ZZiipp ttiimmeess ddoonn''tt iinncclluuddee ttiimmee zzoonnee iinnffoorrmmaattiioonn
QQ:: My file times don't respect time zones. What gives?
AA:: If this is important to you, please submit patches to read the
various Extra Fields that encode times with time zones. I'm just using
the DOS Date/Time, which doesn't have a time zone.
HHooww ddoo II mmaakkee aa sseellff-eexxttrraaccttiinngg ZZiipp
QQ:: I want to make a self-extracting Zip file. Can I do this?
AA:: Yes. You can write a self-extracting archive stub (that is, a
version of unzip) to the output filehandle that you pass to
writeToFileHandle(). See examples/selfex.pl for how to write a self-
extracting archive.
However, you should understand that this will only work on one kind of
platform (the one for which the stub was compiled).
HHooww ccaann II ddeeaall wwiitthh ZZiippss wwiitthh pprreeppeennddeedd ggaarrbbaaggee ((ii..ee.. ffrroomm SSiirrccaamm))
QQ:: How can I tell if a Zip has been damaged by adding garbage to the
beginning or inside the file?
AA:: I added code for this for the Amavis virus scanner. You can query
archives for their 'eocdOffset' property, which should be 0:
if ($zip->eocdOffset > 0)
{ warn($zip->eocdOffset . " bytes of garbage at beginning or within Zip") }
When members are extracted, this offset will be used to adjust the
start of the member if necessary.
CCaann''tt eexxttrraacctt SShhrruunnkk ffiilleess
QQ:: I'm trying to extract a file out of a Zip produced by PKZIP, and
keep getting this error message:
error: Unsupported compression combination: read 6, write 0
AA:: You can't uncompress this archive member. Archive::Zip only supports
uncompressed members, and compressed members that are compressed using
the compression supported by Compress::Zlib. That means only Deflated
and Stored members.
Your file is compressed using the Shrink format, which isn't supported
by Compress::Zlib.
You could, perhaps, use a command-line UnZip program (like the Info-Zip
one) to extract this.
CCaann''tt ddoo ddeeccrryyppttiioonn
QQ:: How do I decrypt encrypted Zip members?
AA:: With some other program or library. Archive::Zip doesn't support
decryption, and probably never will (unless you write it).
HHooww ttoo tteesstt ffiillee iinntteeggrriittyy??
QQ:: How can Archive::Zip can test the validity of a Zip file?
AA:: If you try to decompress the file, the gzip streams will report
errors if you have garbage. Most of the time.
If you try to open the file and a central directory structure can't be
found, an error will be reported.
When a file is being read, if we can't find a proper PK.. signature in
the right places we report a format error.
If there is added garbage at the beginning of a Zip file (as inserted
by some viruses), you can find out about it, but Archive::Zip will
ignore it, and you can still use the archive. When it gets written back
out the added stuff will be gone.
There are two ready-to-use utilities in the examples directory that can
be used to test file integrity, or that you can use as examples for
your own code:
examples/zipcheck.pl shows how to use an attempted extraction to test a
file.
examples/ziptest.pl shows how to test CRCs in a file.
DDuupplliiccaattee ffiilleess iinn ZZiipp??
QQ:: Archive::Zip let me put the same file in my Zip twice! Why don't you
prevent this?
AA:: As far as I can tell, this is not disallowed by the Zip spec. If you
think it's a bad idea, check for it yourself:
$zip->addFile($someFile, $someName) unless $zip->memberNamed($someName);
I can even imagine cases where this might be useful (for instance,
multiple versions of files).
FFiillee oowwnneerrsshhiipp//ppeerrmmiissssiioonnss//AACCLLSS//eettcc
QQ:: Why doesn't Archive::Zip deal with file ownership, ACLs, etc.?
AA:: There is no standard way to represent these in the Zip file format.
If you want to send me code to properly handle the various extra fields
that have been used to represent these through the years, I'll look at
it.
II ccaann''tt ccoommppiillee bbuutt AAccttiivveeSSttaattee oonnllyy hhaass aann oolldd vveerrssiioonn ooff AArrcchhiivvee::::ZZiipp
QQ:: I've only installed modules using ActiveState's PPM program and
repository. But they have a much older version of Archive::Zip than is
in CPAN. Will you send me a newer PPM?
AA:: Probably not, unless I get lots of extra time. But there's no reason
you can't install the version from CPAN. Archive::Zip is pure Perl, so
all you need is NMAKE, which you can get for free from Microsoft (see
the FAQ in the ActiveState documentation for details on how to install
CPAN modules).
MMyy JJPPEEGGss ((oorr MMPP33''ss)) ddoonn''tt ccoommpprreessss wwhheenn II ppuutt tthheemm iinnttoo ZZiippss!!
QQ:: How come my JPEGs and MP3's don't compress much when I put them into
Zips?
AA:: Because they're already compressed.
UUnnddeerr WWiinnddoowwss,, tthhiinnggss lloocckk uupp//ggeett ddaammaaggeedd
QQ:: I'm using Windows. When I try to use Archive::Zip, my machine locks
up/makes funny sounds/displays a BSOD/corrupts data. How can I fix
this?
AA:: First, try the newest version of Compress::Zlib. I know of Windows-
related problems prior to v1.14 of that library.
If that doesn't get rid of the problem, fix your computer or get rid of
Windows.
ZZiipp ccoonntteennttss iinn aa ssccaallaarr
QQ:: I want to read a Zip file from (or write one to) a scalar variable
instead of a file. How can I do this?
AA:: Use "IO::Scalar" and the "readFromFileHandle()" and
"writeToFileHandle()" methods. See "examples/readScalar.pl" and
"examples/writeScalar.pl".
RReeaaddiinngg ffrroomm ssttrreeaammss
QQ:: How do I read from a stream (like for the Info-Zip "funzip"
program)?
AA:: This isn't currently supported, though writing to a stream is.
perl v5.8.8 2004-10-21 Archive::Zip::FAQ(3)