$ time bash -c 'while ((SECONDS < 1)); do :; done' bash -c 'while ((SECONDS < 1)); do :; done' 0.39s user 0.00s system 99% cpu 0.387 total
That can take in between 0 and 1 seconds. Or in other words, $SECONDS becomes 1 in between 0 and 1 second after the shell was started. The reason seems to be because the shell records the value returned by time() upon start-up and $SECONDS expands to time()-that_saved_time. So, if bash is started at 10:00:00.999, then $SECONDS will become 1 only a milisecond after startup while if it's started at 10:00:01.000, $SECONDS will become 1 a full second later. IMO, it would be better if gettimeofday() or equivalent was used instead of time() so that $SECONDS be incremented exactly one second after start-up like ksh93 does. mksh and zsh behave like bash (I'll raise the issue there as well). With zsh (like in ksh93), one can do "typeset -F SECONDS" to make $SECONDS floating point, which can be used as a work around of the "issue". -- Stephane
