• collection: A mongoc_collection_t.
• query: A bson_t containing the query to locate target document(s).
• sort: A bson_t containing the sort order for query.
• update: A bson_t containing an update spec.
• fields: An optional bson_t containing the fields to return or NULL.
• _remove: If the matching documents should be removed.
• upsert: If an upsert should be performed.
• _new: If the new version of the document should be returned.
• reply: Optional pointer to an uninitialized bson_t that will be initialized with the result.
• error: An optional location for a bson_error_t or NULL.

#include <mongoc/mongoc.h>
#include <stdio.h>
int
main (int argc, char *argv[])
{


   mongoc_collection_t *collection;


   mongoc_client_t *client;


   const char *uri_string =


      "mongodb://127.0.0.1:27017/?appname=find-and-modify-example";


   mongoc_uri_t *uri;


   bson_error_t error;


   bson_t *query;


   bson_t *update;


   bson_t reply;


   char *str;


   mongoc_init ();


   uri = mongoc_uri_new_with_error (uri_string, &error);


   if (!uri) {


      fprintf (stderr,


               "failed to parse URI: %s\n"


               "error message:       %s\n",


               uri_string,


               error.message);


      return EXIT_FAILURE;


   }


   client = mongoc_client_new_from_uri (uri);


   if (!client) {


      return EXIT_FAILURE;


   }


   mongoc_client_set_error_api (client, 2);


   collection = mongoc_client_get_collection (client, "test", "test");


   /*


    * Build our query, {"cmpxchg": 1}


    */


   query = BCON_NEW ("cmpxchg", BCON_INT32 (1));


   /*


    * Build our update. {"$set": {"cmpxchg": 2}}


    */


   update = BCON_NEW ("$set", "{", "cmpxchg", BCON_INT32 (2), "}");


   /*


    * Submit the findAndModify.


    */


   if (!mongoc_collection_find_and_modify (collection,


                                           query,


                                           NULL,


                                           update,


                                           NULL,


                                           false,


                                           false,


                                           true,


                                           &reply,


                                           &error)) {


      fprintf (stderr, "find_and_modify() failure: %s\n", error.message);


      return EXIT_FAILURE;


   }


   /*


    * Print the result as JSON.


    */


   str = bson_as_canonical_extended_json (&reply, NULL);


   printf ("%s\n", str);


   bson_free (str);


   /*


    * Cleanup.


    */


   bson_destroy (query);


   bson_destroy (update);


   bson_destroy (&reply);


   mongoc_collection_destroy (collection);


   mongoc_uri_destroy (uri);


   mongoc_client_destroy (client);


   mongoc_cleanup ();


   return EXIT_SUCCESS;
}