R script with user input from command line [duplicate] - r

Question

This question already has answers here:
How to include interactive input in script to be run from the command line
(3 answers)
Closed 5 years ago.
I cannot find a solution to this particular problem, even though more or less similar questions have been questioned before in:
Run R script from command line
http://www.cureffi.org/2014/01/15/running-r-batch-mode-linux/
Running a script from bash is easy enough, however once one needs user interaction I couldn't find a solution. Please consider the example:
userInput<-function(question) {
n = 0
while(n < 1 ){
n <- readline(question)
n <- ifelse(grepl("\\D",n),-1,as.integer(n))
if(is.na(n)){break} # breaks when hit enter
}
return(n)
}
investedLow<- userInput("Invested value in low risk since last time: ")
Now if I save this script as test.R and run it for R --no-save < teste.R the entire script is run and the time for user input does not happen.
The script works fine in Rstudio, for example.
How to wait for user input in a script to be run in the command line?

Answer 1

Here is a total hack, repurposing a very specific purpose-built package for your more-general question:
library(getPass)
userInput<-function(question) {
n = 0
while(n < 1 ){
n <- getPass::getPass(msg = question)
n <- ifelse(grepl("\\D",n),-1,as.integer(n))
if(is.na(n)){break} # breaks when hit enter
}
return(n)
}
investedLow <- userInput("Invested value in low risk since last time: ")
print(investedLow)
Maybe the worst part about this is that getPass hides the user input. There must be a way to modify the source code to fix that.
Update: The getPass author pointed out that the solution could be as simple as using readLines slightly differently:
cat(question)
readLines(file("stdin"), n=1)