External R Session

A permanent R session that runs in the background. This is an R6 class that extends the processx::process class.


r_session$new() creates a new R background process. It can wait for the process to start up (wait = TRUE), or return immediately, i.e. before the process is actually ready to run. In the latter case you may call rs$poll_process() to make sure it is ready.

rs$run() is similar to r(), but runs the function in the rs R session. It throws an error if the function call generated an error in the child process.

rs$run_with_output() is similar to $run(), but returns the standard output and error of the child process as well. It does not throw on errors, but returns a non-zero error member in the result list.

rs$call() starts running a function in the background R session, and returns immediately. To check if the function is done, call the poll_process() method.

rs$get_state() return the state of the R session. Possible values:

  • "starting": starting up,

  • "idle": ready to compute,

  • "busy": computing right now,

  • "finished": the R process has finished.

rs$get_running_time() returns the elapsed time since the R process has started, and the elapsed time since the current computation has started. The latter is NA if there is no active computation.

rs$read() reads an event from the child process, if there is one available. Events might signal that the function call has finished, or they can be progress report events.

r$close() terminates the current computation and the R process. The session object will be in "finished" state after this.


rs <- r_session$new(options = r_session_options(), wait = TRUE,
                     wait_timeout = 3000)

rs$run(func, args = list()) rs$run_with_output(func, args = list()) rs$call(func, args = list())

rs$get_state() rs$get_running_time()

rs$read() rs$close()


  • options: A list of options created via r_session_options().

  • wait: Whether to wait for the R process to start and be ready for running commands.

  • wait_timeout: Timeout for waiting for the R process to start, in milliseconds.

  • func: Function object to call in the background R process. Please read the notes for the similar argument of r()

  • args: Arguments to pass to the function. Must be a list.

  • r_session
rs <- r_ression$new()

rs$run(function() 1 + 2)

rs$call(function() Sys.sleep(1))

# }
Documentation reproduced from package callr, version 3.2.0, License: MIT + file LICENSE

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