Rust

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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Rust


let mime = chilkat::Mime::new();
if mime.load_mime_file("qa_data/message.eml").is_err() {
    println!("{}", mime.last_error_text());
    return;
}

// 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.
let Ok(subject) = mime.get_header_field("Subject") else {
    println!("{}", mime.last_error_text());
    return;
};

println!("Subject: {}", subject);