renameSync method Null safety

Synchronously renames this file.

Returns a File for the renamed file.

If newPath is a relative path, it is resolved against the current working directory (Directory.cwd). This means that simply changing the name of a file, but keeping it the original directory, requires creating a new complete path with the new name at the end. Example:

File changeFileNameOnlySync(File file, String newFileName) {
  var path = file.path;
  var lastSeparator = path.lastIndexOf(Platform.pathSeparator);
  var newPath = path.substring(0, lastSeparator + 1) + newFileName;
  return file.renameSync(newPath);
}

On some platforms, a rename operation cannot move a file between different file systems. If that is the case, instead copySync the file to the new location and then removeSync the original.

If newPath identifies an existing file, that file is removed first. If newPath identifies an existing directory the operation fails and an exception is thrown.