PIXZ FILE INDEX In the (common) special case that pixz is used to compress a tar file, some extra information called the Pixz File Index (PFI) to the end of the output file. The resulting archives are given the suffix .tpxz. The PFI contains an index of which XZ block contains a given tar archive member (file) this allows extraction of an archive member without uncompressing the complete archive, and extremely fast listing compared to a pipeline of xz and tar. Pixz uses a heuristic to detect a tar file and enable the PFI; you can disable this with the -t flag. CAVEATS The PFI takes up a small amount of extra space. Although most tar implementations will ignore the extra data after the end-of-archive marker (for example if extracting with plain xz), there could be some that if causes problems for. If either of these are a problem, the user can disable the adding of PFI with the -t flag. -- David Bremner , Thu, 27 Dec 2012 13:16:40 -0400