Lazarus Pascal

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.

Lazarus Pascal

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Gzip;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  gzip: TGzip;
  inputFile: string;
  outputFile: string;

begin
  success := False;

  //  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.

  gzip := TGzip.Create;

  //  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:
  inputFile := 'example.txt';
  outputFile := 'example.txt.gz';

  //  Compress the file:
  success := gzip.CompressFile(inputFile,outputFile);
  if (success = False) then
    begin
      WriteLn(gzip.LastErrorText);
      Exit;
    end;

  WriteLn('Compression successful.');
  WriteLn('Gzip file created: ' + outputFile);


  gzip.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.