processx (version 1.0.0.9000)

run: Run external command, and wait until finishes

Description

run provides an interface similar to base::system() and base::system2(), but based on the process class. This allows some extra features, see below.

Usage

run(command = NULL, args = character(), commandline = NULL,
  error_on_status = TRUE, echo = FALSE, spinner = FALSE, timeout = Inf,
  stdout_callback = NULL, stderr_callback = NULL, check_interval = 0.01)

Arguments

command

Character scalar, the command to run. It will be escaped via base::shQuote.

args

Character vector, arguments to the command. They will be escaped via base::shQuote.

commandline

A character scalar, a full command line. No escaping will be performed on it.

error_on_status

Whether to throw an error if the command returns with a non-zero status, or it is interrupted. The error clases are system_command_status_error and system_command_timeout_error, respectively, and both errors have class system_command_error as well.

echo

Whether to print the command, the standard output and error to the screen. Note that the order of the standard output and error lines are not necessarily correct, as standard output is typically buffered.

spinner

Whether to a reassusing spinner while the process is running.

timeout

Timeout for the process, in seconds, or as a difftime object. If it is not finished before this, it will be killed.

stdout_callback

NULL, or a function to call for every line of the standard output. See more below.

stderr_callback

NULL, or a function to call for every line of the standard error. See more below.

check_interval

How often to check on the process for output. This is only used if the process had no output at the last check. If a process continuously produces output, then run does not wait at all.

Value

A list with components:

• status The exit status of the process. If this is NA, then the process was killed and had no exit status.
• stdout The standard output of the command, in a character vector.
• stderr The standard error of the command, in a character vector.

Callbacks

Some notes about the callback functions. The first argument of a callback function is a character scalar (length 1 character), a single output or error line. The second argument is always the process object. You can manipulate this object, for example you can call $kill() on it to terminate it, as a response to a message on the standard output or error.

Details

run supports

• Specifying a timeout for the command. If the specified time has passed, and the process is still running, it will be killed (with all its child processes).
• Calling a callback function for each line of the standard output and/or error.

Examples

## Different examples for Unix and Windows
if (.Platform$OS.type == "unix") {
  run("ls")
  system.time(run(commandline = "sleep 10", timeout = 1,
    error_on_status = FALSE))
  system.time(
    run(
      commandline = "for i in 1 2 3 4 5; do echo $i; sleep 1; done",
      timeout=2, error_on_status = FALSE
    )
  )
} else {
  run(commandline = "ping -n 1 127.0.0.1")
  run(commandline = "ping -n 6 127.0.0.1", timeout = 1,
    error_on_status = FALSE)
}