Dart

Compress a File to Gzip with Custom Metadata

See more Gzip Examples

This example demonstrates how to use the CompressFile method to create a Gzip (.gz) file while customizing the metadata embedded in the Gzip header.

Before compression, several properties are set:

• Comment: Adds a descriptive comment to the Gzip file.
• Filename: Specifies the filename to embed in the Gzip data, which may be used by extraction tools as the default output name.
• CompressionLevel: Controls the tradeoff between compression ratio and speed (set to maximum in this example).
• LastModStr: Sets the last-modified timestamp using an RFC 822 formatted date string.

After setting these properties, the input file is compressed and written to a .gz file. This approach allows you to embed meaningful metadata along with the compressed data.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example demonstrates how to compress a file to Gzip format
  // while setting custom metadata such as comment, filename,
  // compression level, and last-modified date.

  final gzip = CkGzip();

  // Set custom Gzip properties:
  gzip.comment = 'Example Gzip file created with Chilkat';
  gzip.filename = 'custom_name.txt';
  gzip.compressionLevel = 9;
  gzip.lastModStr = 'Wed, 1 Apr 2025 12:45:26 -0500';

  // The file to be compressed:
  final inputFile = 'example.txt';
  final outputFile = 'example.txt.gz';

  // Compress the file:
  try {
    gzip.compressFile(inputFile, outputFile);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Compression successful.');
  print('Gzip file created: $outputFile');
}