Question

Suppose I have the following function:

## Just an example
f = function() { 
  for(i in 1:10000)
      cat(i)
  return(1)
}

When I call f() is there a way to stop cat printing to the screen (without altering the function in anyway)?

Reason behind this question

My students upload their R files. I then run the scripts and check to see if they are correct. Every so often, a student leaves in the cat command. This is especially irritating when it’s in a long for loop

Answer 1

On Linux, you can use a sink() call to /dev/null(or to a temporary file on another OS, see ?tempfile) :

sink(file="/dev/null")
f()
sink()