B4X

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.

B4X

Dim success As Boolean = 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.

Dim gzip As ChilkatGzip
gzip.Initialize("gzip")

'  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:
Dim inputFile As String = "example.txt"
Dim outputFile As String = "example.txt.gz"

'  Compress the file:
success = gzip.CompressFile(inputFile, outputFile)
If success = False Then
    Log(gzip.LastErrorText)
    Return
End If


Log("Compression successful.")
Log("Gzip file created: " & outputFile)