R: Run external command, and wait until finishes

run {processx} | R Documentation

## 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(), error_on_status = TRUE,
      wd = NULL, echo_cmd = FALSE, echo = FALSE, spinner = FALSE,
      timeout = Inf, stdout_line_callback = NULL, stdout_callback = NULL,
      stderr_line_callback = NULL, stderr_callback = NULL, env = NULL,
      windows_verbatim_args = FALSE, windows_hide_window = FALSE,
      encoding = "", cleanup_tree = FALSE)

### Arguments

`command` | Character scalar, the command to run.
`args` | Character vector, arguments to the command.
`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.
`wd` | Working directory of the process. If `NULL`, the current working directory is used.
`echo_cmd` | Whether to print the command to run to the screen.
`echo` | Whether to print 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 show a reassuring 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_line_callback` | `NULL`, or a function to call for every line of the standard output. See `stdout_callback` and also more below.
`stdout_callback` | `NULL`, or a function to call for every chunk of the standard output. A chunk can be as small as a single character. At most one of `stdout_line_callback` and `stdout_callback` can be non-`NULL`.
`stderr_line_callback` | `NULL`, or a function to call for every line of the standard error. See `stderr_callback` and also more below.
`stderr_callback` | `NULL`, or a function to call for every chunk of the standard error. A chunk can be as small as a single character. At most one of `stderr_line_callback` and `stderr_callback` can be non-`NULL`.
`env` | Environment of the child process, a named character vector. IF `NULL`, the environment of the parent is inherited.
`windows_verbatim_args` | Whether to omit the escaping of the command and the arguments on windows. Ignored on other platforms.
`windows_hide_window` | Whether to hide the window of the application on windows. Ignored on other platforms.
`encoding` | The encoding to assume for `stdout` and `stderr`. By default the encoding of the current locale is used. Note that `processx` always reencodes the output of both streams in UTF-8 currently.
`cleanup_tree` | Whether to clean up the child process tree after the process has finished.

### 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 or each chunk of the standard output and/or error. A chunk may contain multiple lines, and can be as short as a single character.

### 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 scalar.

- stderr The standard error of the command, in a character scalar.

- timeout Whether the process was killed because of a timeout.

### 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.

### Examples

    ## Different examples for Unix and Windows
    ## Not run:
    if (.Platform$OS.type == "unix") {
      run("ls")
      system.time(run("sleep", "10", timeout = 1,
        error_on_status = FALSE))
      system.time(
        run(
          "sh", c("-c", "for i in 1 2 3 4 5; do echo $i; sleep 1; done"),
          timeout = 2, error_on_status = FALSE
        )
      )
    } else {
      run("ping", c("-n", "1", "127.0.0.1"))
      run("ping", c("-n", "6", "127.0.0.1"), timeout = 1,
        error_on_status = FALSE)
    }

    ## End(Not run)

[Package processx version 3.2.1 Index]