mongo Shell Quick Reference

On this page

• mongo Shell Command History
• Command Line Options
• Command Helpers
• Basic Shell JavaScript Operations
• Keyboard Shortcuts
• Queries
• Error Checking Methods
• Administrative Command Helpers
• Opening Additional Connections
• Miscellaneous
• Additional Resources

mongo Shell Command History

You can retrieve previous commands issued in the mongo shell with the up and down arrow keys. Command history is stored in ~/.dbshell file. See .dbshell for more information.

Command Line Options

The mongo shell can be started with numerous options. See mongo shell page for details on all available options.

The following table displays some common options for mongo:

Option	Description
--help	Show command line options
--nodb	Start mongo shell without connecting to a database. To connect later, see Opening New Connections.
--shell	Used in conjunction with a JavaScript file (i.e. <file.js>) to continue in the mongo shell after running the JavaScript file. See JavaScript file for an example.

Command Helpers

The mongo shell provides various help. The following table displays some common help methods and commands:

Help Methods and Commands	Description
help	Show help.
db.help()	Show help for database methods.
db.<collection>.help()	Show help on collection methods. The <collection> can be the name of an existing collection or a non-existing collection.
show dbs	Print a list of all databases on the server. The operation corresponds to the listDatabases command. If the deployment runs with access control, the operation returns different values based on user privileges. See listDatabases Behavior for details.
use <db>	Switch current database to <db>. The mongo shell variable db is set to the current database.
show collections	Print a list of all collections for current database. SEE ALSO show collections
show users	Print a list of users for current database.
show roles	Print a list of all roles, both user-defined and built-in, for the current database.
show profile	Print the five most recent operations that took 1 millisecond or more. See documentation on the database profiler for more information.
show databases	Print a list of all available databases. The operation corresponds to the listDatabases command. If the deployment runs with access control, the operation returns different values based on user privileges. See listDatabases Behavior for details.
load()	Execute a JavaScript file. See Write Scripts for the mongo Shell for more information.

Basic Shell JavaScript Operations

The mongo shell provides a JavaScript API for database operations.

In the mongo shell, db is the variable that references the current database. The variable is automatically set to the default database test or is set when you use the use <db> to switch current database.

The following table displays some common JavaScript operations:

JavaScript Database Operations	Description
db.auth()	If running in secure mode, authenticate the user.
coll = db.<collection>	Set a specific collection in the current database to a variable coll, as in the following example: copy copied coll = db.myCollection; You can perform operations on the myCollection using the variable, as in the following example: copy copied coll.find();
db.collection.find()	Find all documents in the collection and returns a cursor. See the db.collection.find() and Query Documents for more information and examples. See Iterate a Cursor in the mongo Shell for information on cursor handling in the mongo shell.
db.collection.insertOne()	Insert a new document into the collection.
db.collection.insertMany()	Insert multiple new documents into the collection.
db.collection.updateOne()	Update a single existing document in the collection.
db.collection.updateMany()	Update multiple existing documents in the collection.
db.collection.save()	Insert either a new document or update an existing document in the collection.
db.collection.deleteOne()	Delete a single document from the collection.
db.collection.deleteMany()	Delete documents from the collection.
db.collection.drop()	Drops or removes completely the collection.
db.collection.createIndex()	Create a new index on the collection if the index does not exist; otherwise, the operation has no effect.
db.getSiblingDB()	Return a reference to another database using this same connection without explicitly switching the current database. This allows for cross database queries.

For more information on performing operations in the shell, see:

• MongoDB CRUD Operations
• mongo Shell Methods

Keyboard Shortcuts

The mongo shell provides most keyboard shortcuts similar to those found in the bash shell or in Emacs. For some functions mongo provides multiple key bindings, to accommodate several familiar paradigms.

The following table enumerates the keystrokes supported by the mongo shell:

Keystroke	Function
Up-arrow	previous-history
Down-arrow	next-history
Home	beginning-of-line
End	end-of-line
Tab	autocomplete
Left-arrow	backward-character
Right-arrow	forward-character
Ctrl-left-arrow	backward-word
Ctrl-right-arrow	forward-word
Meta-left-arrow	backward-word
Meta-right-arrow	forward-word
Ctrl-A	beginning-of-line
Ctrl-B	backward-char
Ctrl-C	exit-shell
Ctrl-D	delete-char (or exit shell)
Ctrl-E	end-of-line
Ctrl-F	forward-char
Ctrl-G	abort
Ctrl-J	accept-line
Ctrl-K	kill-line
Ctrl-L	clear-screen
Ctrl-M	accept-line
Ctrl-N	next-history
Ctrl-P	previous-history
Ctrl-R	reverse-search-history
Ctrl-S	forward-search-history
Ctrl-T	transpose-chars
Ctrl-U	unix-line-discard
Ctrl-W	unix-word-rubout
Ctrl-Y	yank
Ctrl-Z	Suspend (job control works in linux)
Ctrl-H (i.e. Backspace)	backward-delete-char
Ctrl-I (i.e. Tab)	complete
Meta-B	backward-word
Meta-C	capitalize-word
Meta-D	kill-word
Meta-F	forward-word
Meta-L	downcase-word
Meta-U	upcase-word
Meta-Y	yank-pop
Meta-[Backspace]	backward-kill-word
Meta-<	beginning-of-history
Meta->	end-of-history

Queries

In the mongo shell, perform read operations using the find() and findOne() methods.

The find() method returns a cursor object which the mongo shell iterates to print documents on screen. By default, mongo prints the first 20. The mongo shell will prompt the user to “Type it” to continue iterating the next 20 results.

The following table provides some common read operations in the mongo shell:

Read Operations	Description
db.collection.find(<query>)	Find the documents matching the <query> criteria in the collection. If the <query> criteria is not specified or is empty (i.e {} ), the read operation selects all documents in the collection. The following example selects the documents in the users collection with the name field equal to "Joe": copy copied coll = db.users; coll.find( { name: "Joe" } ); For more information on specifying the <query> criteria, see Specify Equality Condition.
db.collection.find(<query>, <projection>)	Find documents matching the <query> criteria and return just specific fields in the <projection>. The following example selects all documents from the collection but returns only the name field and the _id field. The _id is always returned unless explicitly specified to not return. copy copied coll = db.users; coll.find( { }, { name: true } ); For more information on specifying the <projection>, see Project Fields to Return from Query.
db.collection.find().sort(<sort order>)	Return results in the specified <sort order>. The following example selects all documents from the collection and returns the results sorted by the name field in ascending order (1). Use -1 for descending order: copy copied coll = db.users; coll.find().sort( { name: 1 } );
db.collection.find(<query>).sort(<sort order>)	Return the documents matching the <query> criteria in the specified <sort order>.
db.collection.find( ... ).limit( <n> )	Limit result to <n> rows. Highly recommended if you need only a certain number of rows for best performance.
db.collection.find( ... ).skip( <n> )	Skip <n> results.
db.collection.count()	Returns total number of documents in the collection.
db.collection.find(<query>).count()	Returns the total number of documents that match the query. The count() ignores limit() and skip(). For example, if 100 records match but the limit is 10, count() will return 100. This will be faster than iterating yourself, but still take time.
db.collection.findOne(<query>)	Find and return a single document. Returns null if not found. The following example selects a single document in the users collection with the name field matches to "Joe": copy copied coll = db.users; coll.findOne( { name: "Joe" } ); Internally, the findOne() method is the find() method with a limit(1).

See Query Documents documentation for more information and examples. See Query and Projection Operators to specify other query operators.

Error Checking Methods

The mongo shell write method integrates the Write Concern directly into the method execution, and returns a WriteResult() object that contains the results of the operation, including any write errors and write concern errors.

Administrative Command Helpers

The following table lists some common methods to support database administration:

JavaScript Database Administration Methods	Description
db.fromColl.renameCollection(<toColl>)	Rename collection from fromColl to <toColl>. See Naming Restrictions.
db.getCollectionNames()	Get the list of all collections in the current database.
db.dropDatabase()	Drops the current database.

See also administrative database methods for a full list of methods.

Opening Additional Connections

You can create new connections within the mongo shell.

The following table displays the methods to create the connections:

JavaScript Connection Create Methods	Description
copy copied db = connect("<host><:port>/<dbname>")	Open a new database connection.
copy copied conn = new Mongo() db = conn.getDB("dbname")	Open a connection to a new server using new Mongo(). Use getDB() method of the connection to select a database.

See also Opening New Connections for more information on the opening new connections from the mongo shell.

Miscellaneous

The following table displays some miscellaneous methods:

Method	Description
Object.bsonsize(<document>)	Prints the BSON size of a <document> in bytes

Additional Resources

Consider the following reference material that addresses the mongo shell and its interface:

• mongo
• mongo Shell Methods
• Database Commands
• Aggregation Reference
• Getting Started Guide

Additionally, the MongoDB source code repository includes a jstests directory which contains numerous mongo shell scripts.