(VBScript) 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.

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Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

' 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.

set gzip = CreateObject("Chilkat.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:
inputFile = "example.txt"
outputFile = "example.txt.gz"

' Compress the file:
success = gzip.CompressFile(inputFile,outputFile)
If (success = 0) Then
    outFile.WriteLine(gzip.LastErrorText)
    WScript.Quit
End If

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

outFile.Close