Detect if a stream support ANSI escape characters

The detection mechanism is as follows:

1. If the cli.ansi option is set to TRUE, TRUE is returned.

2. If the cli.ansi option is set to FALSE, FALSE is returned.

3. If the R_CLI_ANSI environment variable is set to true (case insensitive), then TRUE is returned.

4. If R_CLI_ANSI is not empty and set to false (case insensitive), FALSE is returned.

5. If R is running in the Positron console, then TRUE is returned, with 'positron' added as a name. Positron does not currently support hide/show cursor, scrolling regions, inserting and deleting lines and the alternate screen buffer.

6. Otherwise we autodetect, by checking that all of the following hold:

   • The stream is a terminal, see base::isatty().

   • R is not running inside R.app (the macOS GUI).

   • R is not running inside Emacs.

   • The terminal is not "dumb".

   • stream is either the standard output or the standard error stream.

Usage

is_ansi_tty(stream = "auto")

Arguments

stream

The stream to inspect or manipulate, an R connection object. It can also be a string, one of "auto", "message", "stdout", "stderr". "auto" will select stdout() if the session is interactive and there are no sinks, otherwise it will select stderr().

Value

TRUE or FALSE.

See also

Other terminal capabilities: ansi_hide_cursor(), is_dynamic_tty()

Examples

is_ansi_tty()
#> [1] FALSE