tai64n exits 0 when it sees end of input. It exits 111 without an error message if it has trouble reading stdin or writing stdout.
tai64n does not allocate any memory after it starts.
For example, the timestamp 4000000037c219bf2ef02e94 refers to the nanosecond beginning exactly 935467455.787492500 seconds after the beginning of 1970 TAI; 37c219bf hexadecimal is 935467455, and 2ef02e94 hexadecimal is 787492500.
The current implementation of tai64n relies on the UNIX gettimeofday library routine to return the current time as the number of TAI seconds since 1970-01-01 00:00:10 TAI. Beware that most gettimeofday implementations are not Y2038-compliant. Furthermore, most clocks are not set accurately.