Normally, operations scheduled with later() will not execute unless/until
no other R code is on the stack (i.e. at the top-level). If you need to run
blocking R code for a long time and want to allow scheduled operations to run
at well-defined points of your own operation, you can call run_now() at
those points and any operations that are due to run will do so.
run_now(timeoutSecs = 0L, all = TRUE, loop = current_loop())A logical indicating whether any callbacks were actually run.
Wait (block) for up to this number of seconds waiting for
an operation to be ready to run. If 0, then return immediately if there
are no operations that are ready to run. If Inf or negative, then wait as
long as it takes (if none are scheduled, then this will block forever).
If FALSE, run_now() will execute at most one scheduled
operation (instead of all eligible operations). This can be useful in cases
where you want to interleave scheduled operations with your own logic.
A handle to an event loop. Defaults to the currently-active loop.
If one of the callbacks throws an error, the error will not be caught, and
subsequent callbacks will not be executed (until run_now() is called again,
or control returns to the R prompt). You must use your own
tryCatch if you want to handle errors.