The mongo Shell

Prerequisites

• The MongoDB server must be installed and running before you can connect to it from the mongo shell. Follow the steps in the installation tutorial for your platform to install and start the MongoDB server if required.

• Once you have verified that the mongod server is running, open a terminal window (or a command prompt for Windows) and go to your <mongo shell installation dir> directory:

  cd <mongo shell installation dir>

  Tip

  Adding your <mongo shell installation dir> to the PATH environment variable allows you to type mongo directly instead of having to first go to the <mongo shell installation dir> directory or specify the full path to the binary. Alternatively, you can copy the mongo shell to a location on your filesystem that is already present in your PATH, such as /usr/bin on Linux.

Local MongoDB Instance on Default Port

You can run mongo shell without any command-line options to connect to a MongoDB instance running on your localhost with default port 27017:

mongo

Local MongoDB Instance on a Non-default Port

To explicitly specify the port, include the --port command-line option. For example, to connect to a MongoDB instance running on localhost with a non-default port 28015:

mongo --port 28015

MongoDB Instance on a Remote Host

To explicitly specify the hostname and/or port,

• You can specify a connection string. For example, to connect to a MongoDB instance running on a remote host machine:

  mongo "mongodb://mongodb0.example.com:28015"

• You can use the command-line option --host <host>:<port>. For example, to connect to a MongoDB instance running on a remote host machine:

  mongo --host mongodb0.example.com:28015

• You can use the --host <host> and --port <port> command-line options. For example, to connect to a MongoDB instance running on a remote host machine:

  mongo --host mongodb0.example.com --port 28015

MongoDB Instance with Authentication

To connect to a MongoDB instance requires authentication:

• You can specify the username, authentication database, and optionally the password in the connection string. For example, to connect and authenticate to a remote MongoDB instance as user alice:

  Note

  If you do not specify the password in the connection string, the shell will prompt for the password.

  mongo "mongodb://alice@mongodb0.examples.com:28015/?authSource=admin"

• You can use the --username <user> and --password, --authenticationDatabase <db> command-line options. For example, to connect and authenticate to a remote MongoDB instance as user alice:

  Note

  If you specify --password without the user's password, the shell will prompt for the password.

  mongo --username alice --password --authenticationDatabase admin --host mongodb0.examples.com --port 28015

Connect to a MongoDB Replica Set

To connect to a replica set:

• You can specify the replica set name and members in the connection string.

  mongo "mongodb://mongodb0.example.com.local:27017,mongodb1.example.com.local:27017,mongodb2.example.com.local:27017/?replicaSet=replA"

• If using the DNS Seed List Connection Format, you can specify the connection string:

  mongo "mongodb+srv://server.example.com/"

  Note

  Use of the +srv connection string modifier automatically sets the ssl option to true for the connection.

• You can specify the replica set name and members from the --host <replica set name>/<host1>:<port1>,<host2>:<port2>,... command-line option. For example, to connect to replica set named replA:

  mongo --host replA/mongodb0.example.com.local:27017,mongodb1.example.com.local:27017,mongodb2.example.com.local:27017

TLS/SSL Connection

For TLS/SSL connections,

• You can specify the ssl=true option in the connection string.

  mongo "mongodb://mongodb0.example.com.local:27017,mongodb1.example.com.local:27017,mongodb2.example.com.local:27017/?replicaSet=replA&ssl=true"

• If using the DNS Seed List Connection Format, you can include the +srv connection string modifier:

  mongo "mongodb+srv://server.example.com/"

  Note

  Use of the +srv connection string modifier automatically sets the ssl option to true for the connection.

• You can specify --ssl command-line option. For example, to connect to replica set named replA:

  mongo --ssl --host replA/mongodb0.example.com.local:27017,mongodb1.example.com.local:27017,mongodb2.example.com.local:27017

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()

In addition, you can use the following explicit print methods in the mongo shell:

• print() to print without formatting

• print(tojson(<obj>)) to print with JSON formatting and equivalent to printjson()

• printjson() to print with JSON formatting and equivalent to print(tojson(<obj>))

For more information and examples on cursor handling in the mongo shell, see Iterate a Cursor in the mongo Shell. See also Cursor Help for list of cursor help in the 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 mongo shell waits for the closing parenthesis, closing brace, or the closing bracket before evaluating the code, as in the following example:

> if ( x > 0 ) {
... count++;
... print (x);
... }

You can exit the line continuation mode if you enter two blank lines, as in the following example:

> if (x > 0
...
...
>