How to redirect output of wget as input to unzip?

You have to download your files to a temp file, because (quoting the unzip man page):

Archives read from standard input are not yet supported, except with funzip (and then only the first member of the archive can be extracted).

Just bring the commands together:

wget "http://www.vim.org/scripts/download_script.php?src_id=11834" -O temp.zip
unzip temp.zip
rm temp.zip

But in order to make it more flexible you should probably put it into a script so you save some typing and in order to make sure you don't accidentally overwrite something you could use the mktemp command to create a safe filename for your temp file:

#!/bin/bash
TMPFILE=`mktemp`
PWD=`pwd`
wget "$1" -O $TMPFILE
unzip -d $PWD $TMPFILE
rm $TMPFILE

This is a repost of my answer to a similar question:

The ZIP file format includes a directory (index) at the end of the archive. This directory says where, within the archive each file is located and thus allows for quick, random access, without reading the entire archive.

This would appear to pose a problem when attempting to read a ZIP archive through a pipe, in that the index is not accessed until the very end and so individual members cannot be correctly extracted until after the file has been entirely read and is no longer available. As such it appears unsurprising that most ZIP decompressors simply fail when the archive is supplied through a pipe.

The directory at the end of the archive is not the only location where file meta information is stored in the archive. In addition, individual entries also include this information in a local file header, for redundancy purposes.

Although not every ZIP decompressor will use local file headers when the index is unavailable, the tar and cpio front ends to libarchive (a.k.a. bsdtar and bsdcpio) can and will do so when reading through a pipe, meaning that the following is possible:

wget -qO- http://example.org/file.zip | bsdtar -xvf-

If you have the JDK installed, you can use jar:

wget -qO- http://example.org/file.zip | jar xvf /dev/stdin