Working with Mongo Shell

The mongo shell is an interactive interface to MongoDB. You can use the mongo shell to query and update data as well as perform administrative operations.

The mongo shell is a component of the MongoDB distributions. Once you have installed and have started MongoDB, connect the mongo shell to your running MongoDB instance.

Start the mongo Shell

To start the mongo shell and connect to your MongoDB instance running on localhost with default port:

1. At a prompt in a terminal window, go to your <mongodb installation dir>:

cd <mongodb installation dir>

Type ./bin/mongo to start mongo:

./bin/mongo

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 mongo without any arguments, the 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 examples of starting up mongo and mongo reference which provides details on the available options.

Typically users invoke the shell with the mongo command at the system prompt. Consider the following examples for other scenarios.

Core Options

mongo

--shell
Enables the shell interface. If you invoke the mongo command and specify a JavaScript file as an argument, or use --eval to specify JavaScript on the command line, the --shell option provides the user with a shell prompt after the file finishes executing.

--nodb
Prevents the shell from connecting to any database instances. Later, to connect to a database within the shell, see Opening New Connections.

--norc
Prevents the shell from sourcing and evaluating ~/.mongorc.js on start up.

--quiet
Silences output from the shell during the connection process.

--port <port>
Specifies the port where the mongod or mongos instance is listening. If --port is not specified, mongo attempts to connect to port 27017.

--host <hostname>
Specifies the name of the host machine where the mongod or mongos is running. If this is not specified, mongo attempts to connect to a MongoDB process running on the localhost.

To connect to a replica set, specify the replica set name and a seed list of set members. Use the following form:

<replSetName>/<hostname1><:port>,<hostname2><:port>,<...>

For TLS/SSL connections (--ssl), mongo verifies that the hostname of the mongod or mongos to which you are connecting matches the CN or SAN of the mongod or mongos‘s --sslPEMKeyFile certificate. If the hostname does not match the CN/SAN, mongo will fail to connect.

--eval <javascript>
Evaluates a JavaScript expression that is specified as an argument. mongo does not load its own environment when evaluating code. As a result many options of the shell environment are not available.

--username <username>, -u <username>
Specifies a username with which to authenticate to a MongoDB database that uses authentication. Use in conjunction with the --password and --authenticationDatabase options.

--password <password>, -p <password>
Specifies a password with which to authenticate to a MongoDB database that uses authentication. Use in conjunction with the --username and --authenticationDatabase options. To force mongo to prompt for a password, enter the --password option as the last option and leave out the argument.

--help, -h
Returns information on the options and use of mongo.

--version
Returns the mongo release number.

--verbose
Increases the verbosity of the output of the shell during the connection process.

--disableJavaScriptJIT
New in version 3.2.
Disables use of the JavaScript engine’s JIT compiler.

<file.js>
Specifies a JavaScript file to run and then exit. Generally this should be the last option specified.

To connect to a database on a remote host using authentication and a non-standard port, use the following form:

mongo --username <user> --password <pass> --host <host> --port 28015

Alternatively, consider the following short form:
mongo -u <user> -p <pass> --host <host> --port 28015

Replace <user>, <pass>, and <host> with the appropriate values for your situation and substitute or omit the --port as needed.

Authentication Options

--authenticationDatabase <dbname>

Specifies the database in which the user is created. See Authentication Database.

If you do not specify a value for --authenticationDatabase, mongo uses the database specified in the connection string.

--authenticationMechanism <name>


Working with the mongo Shell

To display the database you are using, type db:

>db

The operation should return test, which is the default database. To switch databases, issue the use <db> helper, as in the following example:

>use <database>


Format Printed Results

The db.collection.find() method returns a cursor to the results; however, in the 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 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:

db.myCollection.find().pretty()

Tab Completion and Other Keyboard Shortcuts

The mongo shell supports keyboard shortcuts. For example,
Use the up/down arrow keys to scroll through command history. See .dbshell 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':
db.myCollection.c<Tab>

Because there are many collection methods starting with the letter 'c', the <Tab> will list the various methods that start with 'c'.

Exit the Shell

To exit the shell, type quit() or use the <Ctrl-c> shortcut.