unshield

unshield [options] <archive_file>

-d <directory>
    Extracts files into the specified directory instead of the current working directory. The directory must exist.

-D
    Do not extract files; only list the contents of the archive. This option is useful for previewing an archive's content.

-g <group>
    Extracts only files belonging to the specified file group within the archive. File groups are defined within the InstallShield project.

-L
    Lists the contents of the InstallShield CAB archive, including file names, sizes, and sometimes file groups.

-O
    Overwrites existing files without prompting for confirmation. Use with caution to avoid accidental data loss.

-v
    Enables verbose output, showing more details during the extraction process, such as files being extracted.

-j
    Do not restore path information; extract all files directly into the target directory, ignoring their original subdirectory structure.

-r
    Recursively extracts embedded CAB files found within the main archive, if any are present.

The unshield command is an open-source utility designed to extract files from proprietary InstallShield CAB (Cabinet) archives. These archives are commonly used in Windows software installers and contain the actual application data.

Unlike standard ZIP or TAR files, InstallShield CAB files employ a unique, often reverse-engineered, format, making them inaccessible by conventional archiving tools. unshield allows Linux and Unix users to inspect, list, or retrieve individual files contained within these installers without needing a Windows environment or commercial InstallShield software. It's particularly useful for reverse engineering, debugging, or accessing specific components of a Windows application package.

unshield primarily works with InstallShield CAB files, which are often embedded within larger InstallShield EXE installers. It cannot directly extract content from the EXE itself unless the CAB files are first manually located and extracted from the EXE. Due to the proprietary and evolving nature of the InstallShield format, some newer versions or highly customized archives might not be fully supported. Users may need to install the unshield package, as it's not a core Linux utility pre-installed on most systems.

On Debian/Ubuntu-based systems, unshield can typically be installed using `sudo apt install unshield`. On other distributions, check your package manager (e.g., `dnf install unshield` for Fedora, `pacman -S unshield` for Arch Linux) as it is usually available in standard repositories.

A common use case involves first extracting the .cab file from a downloaded Windows installer .exe (often using a tool like 7-Zip or cabextract if it's a standard Microsoft CAB). Once the .cab file is isolated, you can then run `unshield <cabinet_file.cab>` to extract its contents to the current directory, or `unshield -d /path/to/extract <cabinet_file.cab>` to specify a destination directory.

The unshield utility emerged as an open-source initiative to address the challenge of accessing files within InstallShield CAB archives on non-Windows operating systems. Developed through reverse engineering the proprietary InstallShield format, it provides a crucial tool for interoperability and data recovery. Its development signifies the open-source community's effort to bypass platform-specific barriers for accessing commonly used software package formats, making Windows installer content accessible on Linux and Unix.

cabextract(1), zip(1), tar(1)