Re: Time-related procedures Lassi Kortela 10 May 2019 11:57 UTC
> 4. Set the timestamp of file F to the current time. I would rather have > a procedure to do precisely this (or a special argument, like giving #t > or #f instead of a numeric timestamp, to denote the present moment). > It's trickier to first get the current time from a C function, then > introduce some delay by going around between Scheme and C, finally > calling another C function to set the timestamp. > > 5. How old is timestamp T? I would have a procedure (age timestamp) that > returns the difference between the current time and the timestamp as > accurately and precisely as it can. These are not as problem-free as I thought. If you want to have a set of timestamps for several files, it may be important that all of them have exactly the same numeric value. In that case, calling (set-file-time-to-current-time filename) for each of them in sequence would mean that they get subtly different timestamps (difference measured in microseconds, maybe even milliseconds it they are on a network file system). In light of this realization I retract my proposal. It is indeed better to be able to ask the OS for a file timestamp denoting the present moment.