The issue is best illustrated with a demo first: ---- # mkdir demo # cd demo # echo '/usr/local/' | pax -rw . (hangs forever, interrupt with Ctrl-C) # echo '/usr/local/' | pax -rw . (this time it completes successfully) ---- In other words, when `pax(1)` is operating under copy mode (the forth synopsis form): ---- pax -r -w [file ...] directory ---- If *all* the following conditions are met, it will hang forever: 1. the `file` operand is not specified; and 2. its has its standard input piped; and 3. the (piped) standard input contains a line that is directory (as the conceptual equivalence of `file` operand); and 4. the `file`(which is a directory) contains at least two components ('*/*/'); and 5. the destination directory does not contain all the parent components of `file`; and 6. the directory is specified with a slash (`/`) at the end.