mongoc_client_read_write_command_with_opts (
   mongoc_client_t *client,
   const char *db_name,
   const bson_t *command,
   const mongoc_read_prefs_t *read_prefs /* UNUSED */,
   const bson_t *opts,
   bson_t *reply,
   bson_error_t *error);

Execute a command on the server, applying logic for commands that both read and 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 both read and write, such as “mapReduce” with an output collection.

Read concern is applied from opts or else from client. Collation is applied from opts (see example for the “distinct” command with opts). Read preferences are not applied. Write concern is applied from opts, or else from client. The write concern is omitted for MongoDB before 3.4.

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

(The mongoc_read_prefs_t parameter was included by mistake when this function was introduced in libmongoc 1.5. A command that writes must not obey a read preference.)


  • 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.
  • read_prefs: Ignored.
  • 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.


See the example code for mongoc_client_read_command_with_opts().