Message within function (for status) not showing immediately in console

Question

I have written a function, which takes some time to run (due to a 1000+ loop on a huge dataset in combination with forecasting model testing).

To have any idea on the status, while the function is called, I use the message command inside the for-loop in the function. The problem is that all the messages are shown in the console after the function is finished, instead of showing immediately. So it doesn't help me :)

I tried to find a solution on Stackoverflow, but didn't found one. I looked for instance on the question "showing a status message in R". All answers and example codes in that topic still give me only text in the console after a function is processed instead of immediately.

How to solve this? Is there maybe a setting in R which prevents immediate printing of message text in the console?

note: examples I tried below, which give the same results as my function; showing text after processing the function.

example1 (Joshua Ulrich):

for(i in 1:10) {
  Sys.sleep(0.2)
  # Dirk says using cat() like this is naughty ;-)
  #cat(i,"\r")
  # So you can use message() like this, thanks to Sharpie's
  # comment to use appendLF=FALSE.
  message(i,"\r",appendLF=FALSE)
  flush.console()
}

example2 (Tyler):

test.message <- function() {
  for (i in 1:9){
    cat(i)
    Sys.sleep(1)
    cat("\b")
  }
}

edit: the first example does work ('flush console' was the problem)...but when I tested it, I commented out flush console for some reason :S

Regarding your second example, you probably need to flush stdout since there's no newline in your string and hence the line may not be printed at once. `flush(stdout())` should do the trick. — fotNelton, Jun 04 '12 at 11:50

Roland · Accepted Answer · 2012-06-04T15:32:40.273

3

test.message <- function() {
     for (i in 1:9){
       cat(paste(as.character(i),'\n'))
       flush.console()
       Sys.sleep(1)
     }
   }

which is similar to the recommendation by fotNelton.

Edit: ttmaccer is most likely right. I've just tested on a Ubuntu server and the code works without flushing the console.

edited Jun 04 '12 at 15:32

answered Jun 04 '12 at 11:57

Roland

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The solution was `flush.console()`... Maybe it is a Windows problem, as ttmaccer answered. But I'm glad it works... – FBE Jun 04 '12 at 15:45
When do we need to use flush.console()? What commands are suggested: show, message, cat, print,...? – skan Mar 20 '17 at 17:27

score 1 · Answer 2 · answered Jun 04 '12 at 15:05

1

I seem to think this maybe a windows specific problem. On linux or running R in a cygwin shell the flush.console() may not be needed.

answered Jun 04 '12 at 15:05

shhhhimhuntingrabbits

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The default on Windows is to buffer the output, the `flush.console` sends the buffered information to the console. The default for linux is to not buffer, so the `flush.console` is not needed, but does not really hurt. – Greg Snow Jun 04 '12 at 15:48

score 0 · Answer 3 · answered Jun 04 '12 at 15:52

You may be interested in using one of the progress bar functions (winProgressBar, tkProgressBar, or txtProgressBar). The win version only works on windows, but the win and tk versions have the advantage that they do not clutter your output, but rather open another small window and display the progress there.

The progress through a loop can be shown with the progress bar, but other detailed information can be updated and shown with the label argument.

Message within function (for status) not showing immediately in console

3 Answers3