pax is POSIX: (: > f;echo "$((0$(pax 2>/dev/null -x ustar -wd -- f|dd 2> /dev/null bs=4 skip=34 count=3|tr -d '\0')))";rm -f f) which might be beneficial

pax is POSIX: (: > f;echo "$((0$(pax 2>/dev/null -x ustar -wd -- f|dd 2> /dev/null bs=4 skip=34 count=3|tr -d '\0')))";rm -f f) which might be beneficial to remember if your file server has a better clock than you do. also, if you're actually targeting POSIX, you should make sure you've set PATH="`getconf PATH`" to guarantee you get the POSIX version of utilities.