Lua

Get a MIME Header Field Value

Demonstrates the Chilkat Mime.GetHeaderField method, which returns the value of the first header field whose name matches case-insensitively. The only argument is the field name; it returns null when no matching field exists.

Note: The file path is relative to the application's current working directory. Absolute paths may also be used. Supply the path to your own file.

Background: This is the everyday way to read a header value — the Subject, a Message-ID, a custom X- header. Because a missing field returns null, the returned value is assigned to a variable and checked rather than used directly, so an absent header is handled cleanly instead of surfacing as an error later. Only the first matching occurrence is returned; iterate by index to see duplicates.

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Lua

local chilkat = require("chilkat")

local mime = chilkat.Mime.new()
local success = mime:load_mime_file("qa_data/message.eml")
if not success then
    print(mime.last_error_text)
    return
end

-- Return the value of the first header field with a matching (case-insensitive) name.
-- GetHeaderField returns null when no matching field exists, so assign it to a string variable
-- and check for success.
local subject = mime:get_header_field("Subject")
if not mime.last_method_success then
    print(mime.last_error_text)
    return
end

print("Subject: " .. subject)