# mongoc_read_concern_append()

## Synopsis

    bool
    mongoc_read_concern_append (mongoc_read_concern_t *read_concern, bson_t *opts);

## Parameters

- `read_concern`: A pointer to a mongoc_read_concern_t.

- `command`: A pointer to a `bson_t`.

## Description

This function appends a read concern to command options. It is useful for appending a read concern to command options before passing them to mongoc_client_read_command_with_opts() or a related function that takes an options document.

## Returns

Returns true on success. If any arguments are invalid, returns false and logs an error.

## Example

See the example code for mongoc_client_read_command_with_opts().