start method Null safety

  1. @override
Future<Process> start(
  1. List<Object> command,
  2. {String? workingDirectory,
  3. Map<String, String>? environment,
  4. bool includeParentEnvironment = true,
  5. bool runInShell = false,
  6. ProcessStartMode mode = ProcessStartMode.normal}
)
override

Starts a process by running the specified command.

The first element in command will be treated as the executable to run, with subsequent elements being passed as arguments to the executable. It is left to implementations to decide what element types they support in the command list.

Returns a Future<Process> that completes with a Process instance when the process has been successfully started. That Process object can be used to interact with the process. If the process cannot be started, the returned Future completes with an exception.

Use workingDirectory to set the working directory for the process. Note that the change of directory occurs before executing the process on some platforms, which may have impact when using relative paths for the executable and the arguments.

Use environment to set the environment variables for the process. If not set, the environment of the parent process is inherited. Currently, only US-ASCII environment variables are supported and errors are likely to occur if an environment variable with code-points outside the US-ASCII range is passed in.

If includeParentEnvironment is true, the process's environment will include the parent process's environment, with environment taking precedence. Default is true.

If runInShell is true, the process will be spawned through a system shell. On Linux and OS X, /bin/sh is used, while %WINDIR%\system32\cmd.exe is used on Windows.

Users must read all data coming on the stdout and stderr streams of processes started with start. If the user does not read all data on the streams the underlying system resources will not be released since there is still pending data.

The following code uses start to grep for main in the file test.dart on Linux.

ProcessManager mgr = new LocalProcessManager();
mgr.start(['grep', '-i', 'main', 'test.dart']).then((process) {
  stdout.addStream(process.stdout);
  stderr.addStream(process.stderr);
});

If mode is ProcessStartMode.normal (the default) a child process will be started with stdin, stdout and stderr connected.

If mode is ProcessStartMode.detached a detached process will be created. A detached process has no connection to its parent, and can keep running on its own when the parent dies. The only information available from a detached process is its pid. There is no connection to its stdin, stdout or stderr, nor will the process' exit code become available when it terminates.

If mode is ProcessStartMode.detachedWithStdio a detached process will be created where the stdin, stdout and stderr are connected. The creator can communicate with the child through these. The detached process will keep running even if these communication channels are closed. The process' exit code will not become available when it terminated.

The default value for mode is ProcessStartMode.normal.

Implementation

@override
Future<Process> start(
  List<Object> command, {
  String? workingDirectory,
  Map<String, String>? environment,
  bool includeParentEnvironment = true,
  bool runInShell = false,
  ProcessStartMode mode = ProcessStartMode.normal,
}) {
  try {
    return Process.start(
      sanitizeExecutablePath(_getExecutable(
        command,
        workingDirectory,
        runInShell,
      )),
      _getArguments(command),
      workingDirectory: workingDirectory,
      environment: environment,
      includeParentEnvironment: includeParentEnvironment,
      runInShell: runInShell,
      mode: mode,
    );
  } on ProcessException catch (exception) {
    throw ProcessPackageException.fromProcessException(exception,
        workingDirectory: workingDirectory);
  }
}