TRUE when R is being used interactively and
An interactive R session is one in which it is assumed that there is a human operator to interact with, so for example R can prompt for corrections to incorrect input or ask what to do next or if it is OK to move to the next plot.
GUI consoles will arrange to start R in an interactive session. When
R is run in a terminal (via
Rterm.exe on Windows), it
assumes that it is interactive if ‘stdin’ is connected to a
(pseudo-)terminal and not if ‘stdin’ is redirected to a file or
pipe. Command-line options --interactive (Unix) and
Rterm.exe) override the default
(On a Unix-alike, whether the
readline command-line editor is
used is not overridden by --interactive.)
Embedded uses of R can set a session to be interactive or not.
Internally, whether a session is interactive determines
how some errors are handled and reported, e.g. see
whether one of --save, --no-save or --vanilla is required, and if R ever asks whether to save the workspace.
the choice of default graphics device launched when needed and
whether graphics devices ever ask for confirmation of a new page.
In addition, R's own R code makes use of
This is a primitive function.