How can I figure out if an R program was executed from the command line

Question

This is what I want:

if (called_from == 'GUI') {
print('Hello GUI')} else {
print('Hello command line')
}

Please let me know if this is possible

Answer 1

Try this code:

if (interactive()) {
  print('Hello GUI')
} else {
  print('Hello command line')
}