C++

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.

C++

#include <CkGzip.h>

void ChilkatSample(void)
    {
    bool 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.

    CkGzip gzip;

    //  Set custom Gzip properties:
    gzip.put_Comment("Example Gzip file created with Chilkat");
    gzip.put_Filename("custom_name.txt");
    gzip.put_CompressionLevel(9);
    gzip.put_LastModStr("Wed, 1 Apr 2025 12:45:26 -0500");

    //  The file to be compressed:
    const char *inputFile = "example.txt";
    const char *outputFile = "example.txt.gz";

    //  Compress the file:
    success = gzip.CompressFile(inputFile,outputFile);
    if (success == false) {
        std::cout << gzip.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Compression successful." << "\r\n";
    std::cout << "Gzip file created: " << outputFile << "\r\n";
    }