r_bg
Evaluate an expression in another R session, in the background
Starts evaluating an R function call in a background R process, and returns immediately.
Usage
r_bg(func, args = list(), libpath = .libPaths(),
repos = default_repos(), stdout = "|", stderr = "|",
poll_connection = TRUE, error = getOption("callr.error", "error"),
cmdargs = c("--slave", "--no-save", "--no-restore"),
system_profile = FALSE, user_profile = FALSE,
env = rcmd_safe_env(), supervise = FALSE, ...)
Arguments
- func
Function object to call in the new R process. The function should be self-contained and only refer to other functions and use variables explicitly from other packages using the
::
notation. The environment of the function is set to.GlobalEnv
before passing it to the child process. Because of this, it is good practice to create an anonymous function and pass that tocallr
, instead of passing a function object from a (base or other) package. In particularr(.libPaths)
does not work, because
.libPaths
is defined in a special environment, butr(function() .libPaths())
works just fine.
- args
Arguments to pass to the function. Must be a list.
- libpath
The library path.
- repos
The repos option. If
NULL
, then no repos option is set. This options is only used ifuser_profile
orsystem_profile
is setFALSE
, as it is set using the system or the user profile.- stdout
The name of the file the standard output of the child R process will be written to. If the child process runs with the
--slave
option (the default), then the commands are not echoed and will not be shown in the standard output. Also note that you need to callprint()
explicitly to show the output of the command(s).- stderr
The name of the file the standard error of the child R process will be written to. In particular
message()
sends output to the standard error. If nothing was sent to the standard error, then this file will be empty. This argument can be the same file asstdout
, in which case they will be correctly interleaved. If this is the string"2>&1"
, then standard error is redictd to standard output.- poll_connection
Whether to have a control connection to the process. This is used to transmit messages from the subprocess to the parent.
- error
What to do if the remote process throws an error. See details below.
- cmdargs
Command line arguments to pass to the R process. Note that
c("-f", rscript)
is appended to this,rscript
is the name of the script file to run. This contains a call to the supplied function and some error handling code.- system_profile
Whether to use the system profile file.
- user_profile
Whether to use the user's profile file.
- env
Environment variables to set for the child process.
- supervise
Whether to register the process with a supervisor. If
TRUE
, the supervisor will ensure that the process is killed when the R process exits.- ...
Extra arguments are passed to the processx::process constructor.
Value
An r_process
object, which inherits from process,
so all process
methods can be called on it, and in addition it also
has a get_result()
method to collect the result.
Examples
# NOT RUN {
rx <- r_bg(function() 1 + 2)
# wait until it is done
rx$wait()
rx$is_alive()
rx$get_result()
# }