An installer created by the InstallShield software stores the files it will install inside of InstallShield Cabinet Files. It would thus be desirable to be able to extract the Microsoft Cabinet Files from the InstallShield Cabinet Files in order to be able to install the applications without access to Microsoft Windows.
The format of InstallShield Cabinet Files is not officially documented but there are two tools available for Microsoft Windows that extracts files from InstallShield installers, and they are distributed with source code included. These tools are named "i5comp" and "i6comp" and can be downloaded from the Internet.
One major drawback with these tools are that for the actual decompression of the files stored in the InstallShield Cabinet Files they require the use of code written by InstallShield that is not available as source code. Luckily, by examining this code with the 'strings' tool, I discovered that they were using the open source zlib library for decompression.
I could have modified i5comp and i6comp to run on other operating systems than Microsoft Windows, but I preferred to use them as a reference for this implementation. The goals of this implementation are:
- Use a well known open source license (MIT)
- Work on both little-endian and big-endian systems
- Separate the implementation in a tool and a library
- Support InstallShield versions 5 and later
- Be able to list contents of InstallShield Cabinet Files
- Be able to extract files from InstallShield Cabinet Files
See the Unshield package for the latest release, or the unshield module in Subversion for the bleeding edge source code!
InstallShield cabinet files vs. Microsoft cabinet files
There are two types of .CAB files: InstallShield cabinet files and Microsoft cabinet files. Unshield only supports the InstallShield cabinets, usually named data1.cab, data1.hdr, data2.cab, etc.
Microsoft cabinet files can be extracted with Stuart Caie's excellent cabextract tool.