mongoc_collection_update_one (mongoc_collection_t *collection,
                              const bson_t *selector,
                              const bson_t *update,
                              const bson_t *opts,
                              bson_t *reply,
                              bson_error_t *error);


  • collection: A mongoc_collection_t.
  • selector: A bson_t containing the query to match the document for updating.
  • update: A bson_t containing the update to perform.
  • reply: Optional. An uninitialized bson_t populated with the update result, or NULL.
  • error: An optional location for a bson_error_t or NULL.

opts may be NULL or a BSON document with additional command options:


This function updates at most one document in collection that matches selector.

To update multiple documents see mongoc_collection_update_many().


Errors are propagated via the error parameter.


Returns true if successful. Returns false and sets error if there are invalid arguments or a server or network error.

A write concern timeout or write concern error is considered a failure.

If provided, reply will be initialized and populated with the fields matchedCount, modifiedCount, and optionally upsertedId if applicable. The reply must be freed with bson_destroy().


#include "mongoc.h"

main (int argc, char **argv)
   bson_t *to_insert = BCON_NEW ("_id", BCON_INT32 (1));
   bson_t *selector = BCON_NEW ("_id", "{", "$gt", BCON_INT32 (0), "}");
   bson_t *update = BCON_NEW ("$set", "{", "x", BCON_INT32 (1), "}");
   const bson_t *next_doc;
   char *to_str;
   bson_error_t err = {0};
   mongoc_cursor_t *cursor;
   mongoc_client_t *client =
      mongoc_client_new ("mongodb://localhost:27017/?appname=example-update");
   mongoc_collection_t *coll =
      mongoc_client_get_collection (client, "db", "example_coll");

   mongoc_client_set_error_api (client, 2);
   /* insert a document */
   if (!mongoc_collection_insert_one (coll, to_insert, NULL, NULL, &err)) {
      fprintf (stderr, "insert failed: %s\n", err.message);
      return EXIT_FAILURE;

   if (!mongoc_collection_update_one (
          coll, selector, update, NULL, NULL, &err)) {
      fprintf (stderr, "update failed %s\n", err.message);
      return EXIT_FAILURE;

   to_str = bson_as_relaxed_extended_json (to_insert, NULL);
   printf ("inserted %s\n", to_str);
   bson_free (to_str);

   cursor = mongoc_collection_find_with_opts (coll, selector, NULL, NULL);
   BSON_ASSERT (mongoc_cursor_next (cursor, &next_doc));
   printf ("after update, collection has the following document:\n");

   to_str = bson_as_relaxed_extended_json (next_doc, NULL);
   printf ("%s\n", to_str);
   bson_free (to_str);

   BSON_ASSERT (mongoc_collection_drop (coll, NULL));

   bson_destroy (to_insert);
   bson_destroy (update);
   bson_destroy (selector);
   mongoc_collection_destroy (coll);
   mongoc_client_destroy (client);
   return EXIT_SUCCESS;