cat function Null safety

Future<CatResult> cat(
  1. List<String> paths,
  2. Object output,
  3. {Stream<List<int>>? input,
  4. List<String>? log,
  5. bool showEnds = false,
  6. bool numberNonBlank = false,
  7. bool showLineNumbers = false,
  8. bool showTabs = false,
  9. bool squeezeBlank = false,
  10. bool showNonPrinting = false}
)

Concatenates files in paths to stdout or File.

  • output should be an IOSink like stdout or a File.
  • input can be stdin.
  • log is used for debugging/testing purposes.

The remaining optional parameters are similar to the GNU cat utility.

Implementation

Future<CatResult> cat(List<String> paths, Object output,
    {Stream<List<int>>? input,
    List<String>? log,
    bool showEnds = false,
    bool numberNonBlank = false,
    bool showLineNumbers = false,
    bool showTabs = false,
    bool squeezeBlank = false,
    bool showNonPrinting = false}) async {
  var result = CatResult();
  var lineNumber = 1;
  log?.clear();
  if (paths.isEmpty) {
    if (input != null) {
      final lines = await _readStream(input);
      try {
        await _writeLines(
            lines,
            lineNumber,
            output,
            log,
            showEnds,
            showLineNumbers,
            numberNonBlank,
            showTabs,
            squeezeBlank,
            showNonPrinting);
      } catch (e) {
        result.addMessage(exitFailure, '$e');
      }
    }
  } else {
    for (final path in paths) {
      try {
        final Stream<String> lines;
        if (path == '-' && input != null) {
          lines = await _readStream(input);
        } else {
          lines = utf8.decoder
              .bind(File(path).openRead())
              .transform(const LineSplitter());
        }
        lineNumber = await _writeLines(
            lines,
            lineNumber,
            output,
            log,
            showEnds,
            showLineNumbers,
            numberNonBlank,
            showTabs,
            squeezeBlank,
            showNonPrinting);
      } on FileSystemException catch (e) {
        final String? osMessage = e.osError?.message;
        final String message;
        if (osMessage != null && osMessage.isNotEmpty) {
          message = osMessage;
        } else {
          message = e.message;
        }
        result.addMessage(exitFailure, message, path: path);
      } on FormatException {
        result.addMessage(exitFailure, 'Binary file not supported.',
            path: path);
      } catch (e) {
        result.addMessage(exitFailure, '$e', path: path);
      }
    }
  }
  return result;
}