Make readline wait for input in R

Question

I\'m trying to make my code ask me for a \"TRUE\" or \"FALSE\" value before proceeding.

It currently works fine if I run it one line at a time, however when I run a

Answer 1

Are you running the code by highlighting the lines and clicking run? If so, that could be your problem because R is line-by-line entering your code in the terminal.

Instead, write your script (or comment out the parts you're not testing) and click the source button. Then R waits for user response instead of inputting the line after readline() into readline().

I had the same problem as you, which prompted me to look for an answer. But then I tried this different method of executing the code and it worked.

Answer 2

If you want to do this in interactive mode then you already have answers but not for use with Rscript. For that instance you need to send messages to the console with cat:

If this test file is named 'prompt.r' and is in the directory where you are working in a system console session:

cat("a string please: ");
a <- readLines("stdin",n=1);
cat("You entered")
 str(a);
cat( "\n" )

Then you can run it from the command line as

$ Rscript prompt.r

If you want an all-purpose script then this would run your script under interactive conditions and my script for non-interactive ones:

if (interactive() ){raw <- 
             readline("TRUE or FALSE -- this is a validation run: ")

                if (raw == "F" | raw == "FALSE" | raw == "False"){
               validation <- F
                 } else{
                     validation <- T
                       }
           rm(raw)  } else{
#  non-interactive
cat("a string please: ");
a <- readLines("stdin",n=1);
cat("You entered")
 str(a);
cat( "\n" )}