mongoc_client_write_command_with_opts (mongoc_client_t *client,
                                       const char *db_name,
                                       const bson_t *command,
                                       const bson_t *opts,
                                       bson_t *reply,
                                       bson_error_t *error);

Execute a command on the server, applying logic that is specific to commands that write, and taking the MongoDB server version into account. To send a raw command to the server without any of this logic, use mongoc_client_command_simple().

Use this function for commands that write such as “drop” or “createRole” (but not for “insert”, “update”, or “delete”, see Basic Write Operations). Write concern and collation can be overridden by various sources. In a transaction, read concern and write concern are prohibited in opts. The highest-priority sources for these options are listed first in the following table. The write concern is omitted for MongoDB before 3.4.

Write Concern






See the example for transactions and for the “distinct” command with opts.

reply is always initialized, and must be freed with bson_destroy().


  • client: A mongoc_client_t.

  • db_name: The name of the database to run the command on.

  • command: A bson_t containing the command specification.

  • opts: A bson_t containing additional options.

  • reply: A location for the resulting document.

  • error: An optional location for a bson_error_t or NULL.

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

Consult the MongoDB Manual entry on Database Commands for each command’s arguments.


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.

Basic Write Operations

Do not use this function to call the basic write commands “insert”, “update”, and “delete”. Those commands require special logic not implemented in mongoc_client_write_command_with_opts. For basic write operations use CRUD functions such as mongoc_collection_insert_one() and the others described in the CRUD tutorial, or use the Bulk API.



Demonstrates how to prepare options for mongoc_client_read_command_with_opts and
mongoc_client_write_command_with_opts. First it calls "cloneCollectionAsCapped"
command with "writeConcern" option, then "distinct" command with "collation" and
"readConcern" options,

Start a MongoDB 3.4 replica set with --enableMajorityReadConcern and insert two

$ mongo
MongoDB Enterprise replset:PRIMARY> db.my_collection.insert({x: 1, y: "One"})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise replset:PRIMARY> db.my_collection.insert({x: 2, y: "Two"})
WriteResult({ "nInserted" : 1 })

Build and run the example:

gcc example-command-with-opts.c -o example-command-with-opts $(pkg-config
--cflags --libs libmongoc-1.0)
./example-command-with-opts [CONNECTION_STRING]
cloneCollectionAsCapped: { "ok" : 1 }
distinct: { "values" : [ 1, 2 ], "ok" : 1 }


#include <mongoc/mongoc.h>
#include <stdio.h>
#include <stdlib.h>

main (int argc, char *argv[])
   mongoc_client_t *client;
   const char *uri_string = "mongodb://";
   mongoc_uri_t *uri;
   bson_t *cmd;
   bson_t *opts;
   mongoc_write_concern_t *write_concern;
   mongoc_read_prefs_t *read_prefs;
   mongoc_read_concern_t *read_concern;
   bson_t reply;
   bson_error_t error;
   char *json;

   mongoc_init ();

   if (argc > 1) {
      uri_string = argv[1];

   uri = mongoc_uri_new_with_error (uri_string, &error);
   if (!uri) {
      fprintf (stderr,
               "failed to parse URI: %s\n"
               "error message:       %s\n",
      return EXIT_FAILURE;

   client = mongoc_client_new_from_uri (uri);
   if (!client) {
      return EXIT_FAILURE;

   mongoc_client_set_error_api (client, 2);

   cmd = BCON_NEW ("cloneCollectionAsCapped",
                   BCON_UTF8 ("my_collection"),
                   BCON_UTF8 ("my_capped_collection"),
                   BCON_INT64 (1024 * 1024));

   /* include write concern "majority" in command options */
   write_concern = mongoc_write_concern_new ();
   mongoc_write_concern_set_wmajority (write_concern, 10000 /* wtimeoutMS */);
   opts = bson_new ();
   mongoc_write_concern_append (write_concern, opts);

   if (mongoc_client_write_command_with_opts (
          client, "test", cmd, opts, &reply, &error)) {
      json = bson_as_canonical_extended_json (&reply, NULL);
      printf ("cloneCollectionAsCapped: %s\n", json);
      bson_free (json);
   } else {
      fprintf (stderr, "cloneCollectionAsCapped: %s\n", error.message);

   bson_free (cmd);
   bson_free (opts);

   /* distinct values of "x" in "my_collection" where "y" sorts after "one" */
   cmd = BCON_NEW ("distinct",
                   BCON_UTF8 ("my_collection"),
                   BCON_UTF8 ("x"),
                   BCON_UTF8 ("one"),

   read_prefs = mongoc_read_prefs_new (MONGOC_READ_SECONDARY);

   /* "One" normally sorts before "one"; make "One" sort after "one" */
   opts = BCON_NEW ("collation",
                    BCON_UTF8 ("en_US"),
                    BCON_UTF8 ("lower"),

   /* add a read concern to "opts" */
   read_concern = mongoc_read_concern_new ();
   mongoc_read_concern_set_level (read_concern,

   mongoc_read_concern_append (read_concern, opts);

   if (mongoc_client_read_command_with_opts (
          client, "test", cmd, read_prefs, opts, &reply, &error)) {
      json = bson_as_canonical_extended_json (&reply, NULL);
      printf ("distinct: %s\n", json);
      bson_free (json);
   } else {
      fprintf (stderr, "distinct: %s\n", error.message);

   bson_destroy (cmd);
   bson_destroy (opts);
   bson_destroy (&reply);
   mongoc_read_prefs_destroy (read_prefs);
   mongoc_read_concern_destroy (read_concern);
   mongoc_write_concern_destroy (write_concern);
   mongoc_uri_destroy (uri);
   mongoc_client_destroy (client);

   mongoc_cleanup ();

   return EXIT_SUCCESS;