Lua

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.

Lua

local chilkat = require("chilkat")

-- 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.

local gzip = chilkat.Gzip.new()

-- Set custom Gzip properties:
gzip.comment = "Example Gzip file created with Chilkat"
gzip.filename = "custom_name.txt"
gzip.compression_level = 9
gzip.last_mod_str = "Wed, 1 Apr 2025 12:45:26 -0500"

-- The file to be compressed:
local inputFile = "example.txt"
local outputFile = "example.txt.gz"

-- Compress the file:
local success = gzip:compress_file(inputFile, outputFile)
if not success then
    print(gzip.last_error_text)
    return
end

print("Compression successful.")
print("Gzip file created: " .. outputFile)