mongoose/docs/http/files.md

title
Serving files

API function mg_serve_http() makes it easy to serve files from a filesystem. Generally speaking, that function is an implementation of the HTTP server that serves static files, CGI and SSI. It's behavior is driven by a list of options that are consolidated into the struct mg_serve_http_opts structure. See struct mg_serve_http_opts definition for the full list of capabilities of mg_serve_http().

For example, in order to create a web server that serves static files from the current directory, implement event handler function as follows:

static void ev_handler(struct mg_connection *c, int ev, void *ev_data) {
  if (ev == MG_EV_HTTP_REQUEST) {
    struct mg_serve_http_opts opts;

    memset(&opts, 0, sizeof(opts);  // Reset all options to defaults
    opts.document_root = ".";       // Serve files from the current directory

    mg_serve_http(c, (struct http_message *) ev_data, s_http_server_opts);
  }
}

See working example at simplest web server.

Sometimes there is no need to implement a full static web server, for example if one works on a RESTful server. If certain endpoints must return the contents of a static file, a simpler mg_http_serve_file() function can be used:

  static void ev_handler(struct mg_connection *c, int ev, void *ev_data) {
   switch (ev) {
     case MG_EV_HTTP_REQUEST: {
       struct http_message *hm = (struct http_message *) ev_data;
       mg_http_serve_file(c, hm, "file.txt",
                          mg_mk_str("text/plain"), mg_mk_str(""));
       break;
     }
     ...
   }
  }