sanitizeFilename method

@useResult String sanitizeFilename({ String replacement = '_', int maxLength = 0, })

Sanitizes this string for use as a filename: removes invalid characters and optional length cap.

Removes or replaces characters that are typically invalid in filenames: \ / : * ? " < > | and control characters. Replaces with replacement (default _). If maxLength is greater than 0, truncates to that length (after sanitization).

Example:

'file:name?.txt'.sanitizeFilename();           // 'file_name_.txt'
'a/b/c'.sanitizeFilename(replacement: '-');    // 'a-b-c'
'long name'.sanitizeFilename(maxLength: 4);   // 'long'

Implementation

@useResult
String sanitizeFilename({
  String replacement = '_',
  int maxLength = 0,
}) {
  if (isEmpty) return this;
  // Common invalid filename chars on Windows and Unix
  final String sanitized = replaceAll(RegExp(r'[\s\\/:*?"<>|\x00-\x1f]'), replacement)
      .replaceAll(RegExp(r'\.{2,}'), replacement) // no ..
      .replaceAll(RegExp(r'^\.+'), replacement); // no leading .
  final String one = RegExp.escape(replacement);
  final String trimmed = sanitized.replaceAll(RegExp('$one+'), replacement).trim();
  if (trimmed.isEmpty) return '';
  if (maxLength > 0 && trimmed.length > maxLength) {
    return trimmed.replaceRange(maxLength, trimmed.length, '');
  }
  return trimmed;
}