C#

Convert a File's Character Encoding from UTF-8 to UFT-8-BOM

See more HTML-to-XML/Text Examples

To add a utf-8 BOM to a file is just a matter of prepending these 3 bytes to the file: 0xEF 0xBB 0xBF.

This may be difficult in some programming languages, or it may be trivial in either. Therefore, the Chilkat solution you see here might be helpful, or in a language such as C++, the Chilkat solution isn't really necessary because it's easy to do yourself.

C#

bool success = false;

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Charset charset = new Chilkat.Charset();

charset.FromCharset = "utf-8";
charset.ToCharset = "bom-utf-8";

success = charset.ConvertFile("qa_data/txt/helloWorld.txt","qa_output/helloWorldBom.txt");
if (success != true) {
    Debug.WriteLine(charset.LastErrorText);
    return;
}

Debug.WriteLine("Success.");