(Tcl) Set a Custom Last-Modified Date in a Gzip File

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This example demonstrates how to use the SetDt method to specify a custom last-modified date and time that will be embedded in a Gzip file.

A CkDateTime object is first initialized with a specific date/time using an RFC 822 formatted string. This date/time is then applied to the Gzip object using SetDt.

When a compression method is called (such as CompressStringToFile), the specified date/time is included in the Gzip metadata. This allows the resulting .gz file to carry a meaningful timestamp rather than using the current system time.

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load ./chilkat.dll

set success 0

# This example demonstrates how to set a custom last-modified date/time
# that will be embedded in a Gzip file.

set gzip [new_CkGzip]

set dt [new_CkDateTime]

# Set the date/time using a timestamp format (ISO 8601 style):
CkDateTime_SetFromTimestamp $dt "2025-11-15T12:45:26-05:00"

# Apply the date/time to the Gzip object:
set success [CkGzip_SetDt $gzip $dt]
if {$success == 0} then {
    puts [CkGzip_lastErrorText $gzip]
    delete_CkGzip $gzip
    delete_CkDateTime $dt
    exit
}

# Compress a string so the custom date/time is embedded in the .gz:
set inputStr "Example text for Gzip compression."
set success [CkGzip_CompressStringToFile $gzip $inputStr "utf-8" "output.gz"]
if {$success == 0} then {
    puts [CkGzip_lastErrorText $gzip]
    delete_CkGzip $gzip
    delete_CkDateTime $dt
    exit
}

puts "Gzip file created with custom last-modified date."

delete_CkGzip $gzip
delete_CkDateTime $dt