in R, can I stop print(cat("")) from returning NULL? and why does cat("foo") return foo>

Question

If I enter

print(cat(""))

I get

NULL

I want to use cat() to print out the progress of an R script, but I don't understand why it is returning NULL at the end of all of my concatenated strings, and more importantly, how to get it to stop?

Answer 1

All your answers are in the documentation for ?cat. The portions that answer your specific question are:

Arguments:

fill: a logical or (positive) numeric controlling how the output is
      broken into successive lines.  If ‘FALSE’ (default), only
      newlines created explicitly by ‘"\n"’ are printed.
      Otherwise, the output is broken into lines with print width
      equal to the option ‘width’ if ‘fill’ is ‘TRUE’, or the value
      of ‘fill’ if this is numeric.  Non-positive ‘fill’ values
      are ignored, with a warning.

... and ...

Value:

 None (invisible ‘NULL’).

So you can't stop print(cat(...)) from returning NULL because that's what cat returns. And you need to explicitly add newlines like cat("foo\n").