* GNU vs posix tar formats
** see "ustar Interchange Format" on the posix standard page for "pax"
** GNU tar supports multiple archive formats, but for the assignment
   you want to focus on ustar
** if correctly formed, your archive can be listed or extracted by GNU tar

* read and write octal
** should be able to just use the octal fprintf format specifier

* how are symlinks represented in the tar file
** prefix/name is the path to the symlink
** linkname is the path _in_ the symlink
** all the other metadata in the ustar header is about the symlink

* note about multiple hard links?
** tar handles the case of multiple hardlinks to the same file optimaly
   meaning, only put the content in once
** you don't have to do that