tai64nunix converts precise TAI64N timestamps to a unix-time approximation. It works much like tai64nlocal delivered within D.J.B's daemontools package. All restrictions of tai64nlocal apply to tai64nunix, too.
Download tai64nunix-1.1.1.tar.gz
and extract it in a temporary directory.
to compile, enter
make make setup check
It will install the tai64nunix program in /usr/local/bin and add a symlink to /command.
tai64nunix reads lines from stdin. If a line does not begin with @, tai64nunix writes it to stdout without change. If a line begins with @, tai64nunix looks for a timestamp after the @, in the format printed by tai64n, and writes the line to stdout with the timestamp converted to local time in unix time format: seconds since Epoch. For example, in the US/Pacific time zone, the input line
@4000000037c219bf2ef02e94 mark
should be printed as
935467445 mark