[jpstewart]

The thing that always trips me up (coming from Linux) is that GNU tar supports z, j, and J options (among others) to filter through the gzip, bzip2, and xz compression programs respectively. IRIX tar doesn't support any of the compression options. You have to use a pipe or an intermediate file to manually compress/decompress after/before the tar command.

The gzip, bzip2, and xz utilities aren't even part of the base IRIX install. You need to install the SGI freeware packages (which IIRC do not include xz), or Nekoware, or compile them from source.