public static String execCommand(String... cmd) throws IOException {
    return new ShellCommand(cmd).run();
  }
@Test
  public void execCommand() throws Exception {
    String testString = "alluxio";
    // Execute echo for testing command execution.
    String result = ShellUtils.execCommand("bash", "-c", "echo " + testString);
    assertEquals(testString + "\n", result);
  }