(Tcl) Retrieve Metadata from a Gzip File

See more Gzip Examples

This example demonstrates how to use the GetGzipInfo method to retrieve metadata embedded within a Gzip file.

The method reads the Gzip header and extracts any available metadata, including the embedded filename, comment, and optional extra data. The extracted information is returned in a JsonObject.

Because these fields are optional, the example checks for the existence of each JSON member using HasMember before retrieving its value. This avoids attempting to access values that may not be present.

Note: This example requires Chilkat v11.5.0 or greater.

Chilkat Tcl Extension Downloads Chilkat Tcl Extension Downloads

load ./chilkat.dll

set success 0

# This example demonstrates how to retrieve metadata embedded in a Gzip file.

set gzip [new_CkGzip]

set json [new_CkJsonObject]

# The Gzip file to examine:
set gzPath "example.txt.gz"

# Get the metadata information:
set success [CkGzip_GetGzipInfo $gzip $gzPath $json]
if {$success == 0} then {
    puts [CkGzip_lastErrorText $gzip]
    delete_CkGzip $gzip
    delete_CkJsonObject $json
    exit
}

# Output the JSON containing metadata:
puts "Gzip metadata JSON:"
puts [CkJsonObject_emit $json]

# Access individual fields only if they exist:

if {[CkJsonObject_HasMember $json "filename"] == 1} then {
    set filename [CkJsonObject_stringOf $json "filename"]
    puts "Filename: $filename"
}

if {[CkJsonObject_HasMember $json "comment"] == 1} then {
    set comment [CkJsonObject_stringOf $json "comment"]
    puts "Comment: $comment"
}

if {[CkJsonObject_HasMember $json "extraData"] == 1} then {
    set extraData [CkJsonObject_stringOf $json "extraData"]
    puts "ExtraData (Base64): $extraData"
}


delete_CkGzip $gzip
delete_CkJsonObject $json