On Wed, Feb 19, 2020 at 07:24:06AM -0600, Richard Owlett wrote: > I'm looking for a tutorial covering > "cron(3tcl) cron" [.../tcllib/cron.3tcl.en.html] > NOT "CRON(8) System Manager's Manual" [.../cron/cron.8.en.html]
cron(3tcl) is a Tcl library (or module or what it's ever called), not a command. So it's to be used from a Tcl program. It schedules actions at given times whithin a running Tcl program and is not based on its namesake (just inspired on it). That said, "man 3tcl cron" should lead you to the man page. One of Tcl's niceties is that its docs are available as man pages). I don't know whether there is any tutorial on that around (I don't even know whether Tcl's cron is what you are after -- guessing from your question it's not clear to me). A quick search of cron in https://wiki.tcl.tk doesn't yield good hits -- only two describing how to interact with the system cron, i.e. the "real thing". > Neither DuckDuckGo nor Google gave acceptable references. > Many were references to cron(8) *NOT* cron(3tcl). > > A website of interest updates data hourly. > There is an internal time stamp in the data. > There is a significant, but a to be determined, delay between the > time-stamp and when the data is available on the web. > > I want to do data captures at 1 minute intervals from 10 minutes > before to 10 minutes after the top of the hour. And you want to control all of that from a constantly running Tcl process (so some kind of daemon)? If your answer is "yes", then cron(3tcl) might be for you (OTOH it's pretty straightforward to schedule timing things from Tcl without a special library, so perhaps understanding cron(3tcl) ends up being more complex than cooking something up around [after]). If your answer is "no", then that's not the cron for you. My Tcl is a bit rusty, but if you're still on the "yes" branch above, you can show us the code you already tried and we can try to take it from there. Cheers -- tomás
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