rename method - File class - dart:io library - Dart API

// Renames this file.

// Returns a Future<File> that completes with a File for the renamed file.

// If newPath is a relative path, it is resolved against the current working directory (Directory.current). 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:

Future<File> changeFileNameOnly(File file, String newFileName) {
  var path = file.path;
  var lastSeparator = path.lastIndexOf(Platform.pathSeparator);
  var newPath = path.substring(0, lastSeparator + 1) + newFileName;
  return file.rename(newPath);
}

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

// If newPath identifies an existing file, that file is removed first. If newPath identifies an existing directory, the operation fails and the future completes with an exception.

// Implementation
Future<File> rename(String newPath);