CODEWITHSUNDEEP
r
highBandWidth
highBandWidth

Reputation: 17321

How to include interactive input in script to be run from the command line

I am trying to write an interactive R script. For example:

try.R:

print("Entr some numbers. >",quote=F)
a = scan(what=double(0))
print a
q()

Now, if I run it on the command line as

$ R --no-save < try.R

It tries to get the stdin from try.R, giving the following error:

> print("Entr some numbers. >",quote=F)
[1] Entr some numbers. >
> a = scan(what=double(0))
1: print a
Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings,  : 
  scan() expected 'a real', got 'print'
Execution halted

I tried a few other methods but they all give errors. For example:

$ R CMD BATCH try.R 
$ Rscript try.R

So how do I write an R script that works from the *nix shell command line, and can take in interactive input from the user?

Upvotes: 17

Views: 30824

Answers (3)

Christian David
Christian David

Reputation: 465

The answer by @Joshua Ulrich is fine for Linux, but hangs under macOS and needs to be terminated using Ctrl-D.

This is a work-around for both Linux and macOS:

#!/usr/bin/env Rscript

print(system("read -p 'Prompt: ' input; echo $input", intern = TRUE))

Upvotes: 0

Paulo S. Abreu
Paulo S. Abreu

Reputation: 193

What worked for me on Windows with RStudio 0.98.945 and R version 3.1.1 was:

    cat("What's your name? ")
    x <- readLines(con=stdin(),1)
    print(x)

Upvotes: 4

Joshua Ulrich
Joshua Ulrich

Reputation: 176648

Try this:

cat("What's your name? ")
x <- readLines(file("stdin"),1)
print(x)

Hopefully some variant of that works for you.

Upvotes: 22

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