Zig

Get the Content-ID of an Attachment

Demonstrates the Chilkat Email.GetAttachmentContentID method, which returns the Content-ID header field for the Nth attachment. The index is zero-based, so the first attachment is 0. This example adds an attachment and reads its Content-ID (which may be empty when none was assigned).

Background: A Content-ID is a unique identifier for a MIME part. It is essential for inline "related" resources, where HTML references an image by cid:, but ordinary file attachments usually have none. Reading it is useful when inspecting how a message is assembled, or when distinguishing parts that are referenced from the body versus those meant purely as downloadable attachments.

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const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    // Demonstrates the GetAttachmentContentID method, which returns the Content-ID header
    // field for the Nth attachment.  The index is zero-based (the first attachment is 0).

    const email = try chilkat.Email.init();
    defer email.deinit();
    email.setSubject("Attachment Content-ID");

    email.addStringAttachment("notes.txt", "Some notes.") catch {};

    // Get the Content-ID of the first attachment (may be empty if none was assigned).
    const cid = try email.getAttachmentContentID(alloc, 0);
    std.debug.print("Attachment 0 Content-ID: {s}\n", .{cid});
}