How to convert from rar or tgz to squashfs without having to extract to temporary folder?

I enjoy using squashfs for compression because of the simplicity of mounting them as loop devices to access the files inside. I have a lot of rar, tgz and zip files that I would like to convert to squashfs. In this answer , I saw that it is possible to use a pseudo file when compressing a disk image to squashfs to avoid having to use a temporary file the size of the whole disk. mkdir empty-dir mksquashfs empty-dir squash.img -p 'sda_backup.img f 444 root root dd if=/dev/sda bs=4M' I would like to use pseudo files to convert from rar, tgz or zip to squashfs in the same way (on the fly), so I don't have to first extract the whole archive to disk and then compress to squashfs in a separate operation. Some of these archives contain thousands of individual files, some of which will have spaces or other special characters in their filenames. I looked at the README , and I think I would need to use the -pf option, but I'm not sure how to create the pseudo file on the fly (and also not have problems with filenames with spaces). I think I would need to use process substitution to create the list of files from the source archive. Ideally I would like to have a command that is able to convert any rar, tgz or zip without having to individually create the pseudo file for each archive, but if anyone can tell me how I can do it with one of those archive formats, then hopefully I can work it out for the others. Thanks everyone.