• 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.

• writeConcern: Construct a mongoc_write_concern_t and use mongoc_write_concern_append to add the write concern to opts. See the example code for mongoc_client_write_command_with_opts.
• sessionId: First, construct a mongoc_client_session_t with mongoc_client_start_session. You can begin a transaction with mongoc_client_session_start_transaction, optionally with a mongoc_transaction_opt_t that overrides the options inherited from collection, and use mongoc_client_session_append to add the session to opts. See the example code for mongoc_client_session_t.
• validate: Construct a bitwise-or of all desired bson_validate_flags_t. Set to false to skip client-side validation of the provided BSON documents.
• bypassDocumentValidation: Set to true to skip server-side schema validation of the provided BSON documents.
• collation: Configure textual comparisons. See Setting Collation Order, and the MongoDB Manual entry on Collation. Collation requires MongoDB 3.2 or later, otherwise an error is returned.
• upsert: When true, creates a new document if no document matches the query.
• arrayFilters: An array of filters specifying to which array elements an update should apply.

#include "mongoc/mongoc.h"
int
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 error = {0};


   mongoc_cursor_t *cursor;


   mongoc_client_t *client;


   mongoc_collection_t *coll;


   const char *uri_string = "mongodb://localhost:27017/?appname=example-update";


   mongoc_uri_t *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;


   }


   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, &error)) {


      fprintf (stderr, "insert failed: %s\n", error.message);


      return EXIT_FAILURE;


   }


   if (!mongoc_collection_update_one (


          coll, selector, update, NULL, NULL, &error)) {


      fprintf (stderr, "update failed: %s\n", error.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_uri_destroy (uri);


   mongoc_client_destroy (client);


   return EXIT_SUCCESS;
}