I have a file which I'm told is a compressed bitstream.

Any commands like lz4cat to deal with it? I want to decode it and things like unzip won't work because of the bitstream component.

Unless you know which compression format is being used you won't know which command to use.

Who told you it is a compressed bitstream and is there more information on the subject ?

Does the `file` command tell you anything about the compression used ?

Also it is very unlikely that unzip would be used as zip is a compression utility itself. You wouldn't compress the output of zip again. It is likely a tar or cpio archive that is then output to standard output and compressed through a pipe.

This approach is often used to create an initramfs as follows.

find . | cpio --quiet -c -o | gzip -9 -n > ../initramfs64-catalyst

To extract the above you would do the following

zcat initramfs64-catalyst | cpio -id