You can extract the contents of a .deb package file without opening it on Debian or Ubuntu Linux using the dpkg-deb command line tool. The following command will extract the contents of a .deb package file named package.deb to the directory extracted_files:
dpkg-deb -R package.deb extracted_files
The -R option tells dpkg-deb to extract the contents of the package to the specified directory. The contents of the package, including its control information and files, will be extracted to the extracted_files directory.