void validate() throws IOException {
    if (inputStream == null) {
      inputStream = System.in;
    }
    TinkeyUtil.validateFormat(inFormat);
    if (credentialPath != null) {
      Validators.validateExists(new File(credentialPath));
    }
  }
Common args for commands that read from file.
tools/tinkey/src/main/java/com/google/crypto/tink/tinkey/InOptions.java