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

Question

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?

Answer 1

Try this:

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

Hopefully some variant of that works for you.