Although ISO files are a very convenient way to distribute software, then can often be very large, perhaps gigabytes in size. And if you only need maybe one or two files from the image, having to download the whole thing first will probably seem just a little annoying.

There could be an alternative, though. Re7zip is an interesting Java-based tool which can remotely extract files from an http-hosted archive, without having to download the full archive first – and in some situations that could save you an enormous amount of time.

The program is based around 7zip, as you might guess from the name, and that means it’s not restricted to ISO files. Rather, you’re able to access everything that 7zip can, a very lengthy list of formats: 7z, XZ, BZIP2, GZIP, TAR, ZIP, WIM, ARJ, CAB, CHM, CPIO, CramFS, DEB, DMG, FAT, HFS, ISO, LZH, LZMA, MBR, MSI, NSIS, NTFS, RAR, RPM, SquashFS, UDF, VHD, WIM, XAR and Z.

re7zip is fussy about syntax, making it less than easy to use

What you don’t get here is 7zip’s ease of use, unfortunately. Re7zip has to be run from the command line, and isn’t quite as straightforward as we’d like.

A typical remote extraction might look something like this.

java -java re7zip.jar /t=iso /a=http://www.site.com/folder/file.iso /e=folder\file.txt /o=file.txt

Here the /t switch tells the program the type of your archive; /a points to the archive you’d like to access; /e highlights the file within the archive which you’d like to extract, and /o indicates the output file name you’d like to generate locally.

As command lines go, this isn’t exactly complex, but one problem here is that re7zip is rather strict about its syntax. During testing we omitted the /o switch, for instance, thinking the program would simply keep the original file name when it saved the downloaded copy. But no, it just didn’t work (and there was no clear explanation about why, either).

And of course one major limitation with all this is that you have to know the precise name and location of the file you’d like to extract from your archive. It would be enormously helpful if you could ask Re7zip to display the contents of a specified remote archive, but unfortunately that option isn’t yet available.

For all this, re7zip is still an excellent tool. There’s no hassles with installation (it’s a single file), you get support for a host of archive types, and in some situations it could save you a huge amount of time. There is also plenty of scope to make the program even better, though, and we hope the author will revisit and enhance it in the future.