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The ``mongo`` Shell
.. default-domain:: mongodb
.. contents:: On this page
:backlinks: none
:depth: 1
:class: singlecol
The :program:`mongo` shell is an interactive JavaScript interface to
MongoDB. You can use the :program:`mongo` shell to query and update
data as well as perform administrative operations.
The :program:`mongo` shell is a component of the `MongoDB distributions
<>`_. Once you have :doc:`installed and
have started MongoDB </installation>`, connect the :program:`mongo`
shell to your running MongoDB instance.
Most examples in the :doc:`MongoDB Manual </index>` use the
:program:`mongo` shell; however, many :doc:`drivers
</applications/drivers>` provide similar interfaces to MongoDB.
Start the ``mongo`` Shell
.. important::
Ensure that MongoDB is running before attempting to start the
:program:`mongo` shell.
To start the :program:`mongo` shell and connect to your :doc:`MongoDB
</reference/program/mongod>` instance running on **localhost** with
**default port**:
#. At a prompt in a terminal window (or a command prompt for Windows),
go to your ``<mongodb installation dir>``:
.. code-block:: sh
cd <mongodb installation dir>
#. Type ``./bin/mongo`` to start :program:`mongo`:
.. code-block:: sh
If you have added the ``<mongodb installation dir>/bin`` to the
``PATH`` environment variable, you can just type ``mongo`` instead
of ``./bin/mongo``.
When you run :program:`mongo` without any arguments, the
:program:`mongo` shell will attempt to connect to the MongoDB instance
running on the ``localhost`` interface on port ``27017``. To specify a
different host or port number, as well as other options, see
:ref:`examples of starting up mongo <mongo-usage-examples>` and
:doc:`mongo reference </reference/program/mongo>` which provides
details on the available options.
``.mongorc.js`` File
When starting, :program:`mongo` checks the user's :envvar:`HOME`
directory for a JavaScript file named :ref:`.mongorc.js
<mongo-mongorc-file>`. If found, :program:`mongo` interprets the
content of :file:`.mongorc.js` before displaying the prompt for the
first time. If you use the shell to evaluate a JavaScript file or
expression, either by using the :option:`--eval <mongo --eval>`
option on the command line or by specifying :ref:`a .js file to
mongo <mongo-shell-file>`, :program:`mongo` will read the
``.mongorc.js`` file *after* the JavaScript has finished processing.
You can prevent ``.mongorc.js`` from being loaded by using the
:option:`--norc` option.
.. _mongo-shell-executing-queries:
Working with the ``mongo`` Shell
To display the database you are using, type ``db``:
.. code-block:: sh
The operation should return ``test``, which is the default database.
To switch databases, issue the ``use <db>`` helper, as in the
following example:
.. code-block:: javascript
use <database>
To list the available databases, use the helper ``show dbs``. See also
:method:`db.getSiblingDB()` method to access a different database from
the current database without switching your current database context
(i.e. ``db``).
You can switch to non-existing databases. When you first store data in
the database, such as by creating a collection, MongoDB creates the
database. For example, the following creates both the database
``myNewDatabase`` and the :term:`collection` ``myCollection`` during
the :method:`~db.collection.insert()` operation:
.. code-block:: javascript
use myNewDatabase
db.myCollection.insert( { x: 1 } );
The :method:`db.myCollection.insert() <db.collection.insert()>` is one
of the :doc:`methods available in the mongo shell </reference/method>`
- ``db`` refers to the current database.
- ``myCollection`` is the name of the collection.
If the :program:`mongo` shell does not accept the name of the
collection, for instance if the name contains a space, hyphen, or
starts with a number, you can use an alternate syntax to refer to the
collection, as in the following:
.. code-block:: javascript
For more documentation of basic MongoDB operations in the
:program:`mongo` shell, see:
- :gettingstarted:`Getting Started Guide </shell>`
- :doc:`/tutorial/insert-documents`
- :doc:`/tutorial/query-documents`
- :doc:`/tutorial/modify-documents`
- :doc:`/tutorial/remove-documents`
- :doc:`/reference/method`
Format Printed Results
The :method:`db.collection.find()` method returns a :term:`cursor` to
the results; however, in the :program:`mongo` shell, if the returned
cursor is not assigned to a variable using the ``var`` keyword, then
the cursor is automatically iterated up to 20 times to print up to the
first 20 documents that match the query. The :program:`mongo` shell
will prompt ``Type it`` to iterate another 20 times.
To format the printed result, you can add the ``.pretty()`` to the
operation, as in the following:
.. code-block:: javascript
In addition, you can use the following explicit print methods in the
:program:`mongo` shell:
- ``print()`` to print without formatting
- ``print(tojson(<obj>))`` to print with :term:`JSON` formatting and
equivalent to ``printjson()``
- ``printjson()`` to print with :term:`JSON` formatting and equivalent
to ``print(tojson(<obj>))``
For more information and examples on cursor handling in the
:program:`mongo` shell, see :doc:`/core/cursors`. See also
:ref:`mongo-shell-help-cursor` for list of cursor help in the
:program:`mongo` shell.
Multi-line Operations in the ``mongo`` Shell
If you end a line with an open parenthesis (``'('``), an open brace
(``'{'``), or an open bracket (``'['``), then the subsequent lines start
with ellipsis (``"..."``) until you enter the corresponding closing
parenthesis (``')'``), the closing brace (``'}'``) or the closing
bracket (``']'``). The :program:`mongo` shell waits for the closing
parenthesis, closing brace, or the closing bracket before evaluating
the code, as in the following example:
.. code-block:: javascript
> if ( x > 0 ) {
... count++;
... print (x);
... }
You can exit the line continuation mode if you enter two blank
lines, as in the following example:
.. code-block:: javascript
> if (x > 0
Tab Completion and Other Keyboard Shortcuts
The :program:`mongo` shell supports keyboard shortcuts. For example,
- Use the up/down arrow keys to scroll through command history. See
:ref:`.dbshell <mongo-dbshell-file>` documentation for more
information on the ``.dbshell`` file.
- Use ``<Tab>`` to autocomplete or to list the completion
possibilities, as in the following example which uses ``<Tab>`` to
complete the method name starting with the letter ``'c'``:
.. code-block:: javascript
Because there are many collection methods starting with the letter
``'c'``, the ``<Tab>`` will list the various methods that start with
For a full list of the shortcuts, see :ref:`Shell Keyboard Shortcuts
.. _mongo-shell-exit:
Exit the Shell
To exit the shell, type ``quit()`` or use the ``<Ctrl-c>`` shortcut.
.. seealso::
- :gettingstarted:`Getting Started Guide </shell>`
- :program:`mongo Reference Page <mongo>`
.. class:: hidden
.. toctree::
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