Display a time clock in the R command line

Question

I wonder if there is a way to display the current time in the R command line, like in MS DOS, we can use

Prompt $T $P$G 

to include the time clock in every prompt line. Something like

options(prompt=paste(format(Sys.time(), "%H:%M:%S"),"> ")) 

will do it, but then it is fixed at the time it was set. I'm not sure how to make it update automatically.

Answer 1

Chase points the right way as options("prompt"=...) can be used for this. But his solutions adds a constant time expression which is not what we want.

The documentation for the function taskCallbackManager has the rest:

R> h <- taskCallbackManager() R> h$add(function(expr, value, ok, visible) {  +     options("prompt"=format(Sys.time(), "%H:%M:%S> "));  +             return(TRUE) },  +     name = "simpleHandler") [1] "simpleHandler" 07:25:42> a <- 2 07:25:48> 

We register a callback that gets evaluated after each command completes. That does the trick. More fancy documentation is in this document from the R developer site.

Answer 2

None of the other methods, which are based on callbacks, will update the prompt unless a top-level command is executed. So, pressing return in the console will not create a change. Such is the nature of R's standard callback handling.

If you install the tcltk2 package, you can set up a task scheduler that changes the option() as follows:

library(tcltk2) tclTaskSchedule(1000, {options(prompt=paste(Sys.time(),"> "))}, id = "ticktock", redo = TRUE) 

Voila, something like the MS DOS prompt.

NB: Inspiration came from this answer.

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Note 1: The wait time (1000 in this case) refers to the # of milliseconds, not seconds. You might adjust it downward when sub-second resolution is somehow useful.